Deprecate QRep and XMin mirror types

Mark the Query Replication (QRep) and XMin mirror types as deprecated; CDC
is the recommended, actively-maintained mirror type. They remain fully
functional and no code is currently being removed.

- ui/app/api/mirror-types: flag QRep and XMin cards as deprecated.
- ui/app/mirrors/create/mirrorcards: render a "Deprecated" badge on those
  cards in the create-mirror flow.
- README: add a mirror-type deprecation notice; soften "no code is being
  removed" to "currently" across the connector/mirror notices.
- CONTRIBUTING.md, docs/deprecated-connectors.md: same "currently" wording.

Refs #4465

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Jeremyyang920

CONTRIBUTING.md

@@ -4,6 +4,6 @@ Thanks for your interest in contributing to PeerDB! Bug reports, feature request
 
 ## Deprecated connectors
 
-Several destination connectors (Snowflake, BigQuery, ElasticSearch, Kafka including Confluent and Redpanda, Azure Event Hubs, Google Pub/Sub, and S3) are deprecated and no longer actively maintained. They remain fully functional, and no code is being removed. (BigQuery is deprecated only as a destination — it remains a supported source.)
+Several destination connectors (Snowflake, BigQuery, ElasticSearch, Kafka including Confluent and Redpanda, Azure Event Hubs, Google Pub/Sub, and S3) are deprecated and no longer actively maintained. They remain fully functional, and no code is currently being removed. (BigQuery is deprecated only as a destination — it remains a supported source.)
 
 If you depend on one of these connectors, see the [deprecated connectors migration guide](docs/deprecated-connectors.md) for how to pin to a release or fork the relevant connector code.

README.md

@@ -17,7 +17,9 @@ At PeerDB, we are building a fast, simple and the most cost effective way to str
 
 We support different modes of streaming - log based (CDC), cursor based (timestamp or integer) and XMIN based. Performance wise, we are 10x faster than existing tools. Features wise, we support native Postgres features such as comprehensive set of data-types incl. jsonb/arrays/geospatial, efficiently streaming TOAST columns, schema changes and so on.
 
-> **Connector deprecation notice:** The Snowflake, BigQuery, ElasticSearch, Kafka (including Confluent and Redpanda variants), Azure Event Hubs, Google Pub/Sub, and S3 **destination** connectors are deprecated and no longer actively maintained. They remain fully functional in the current and all prior releases, and no code is being removed. The actively-maintained paths going forward are Postgres → ClickHouse, Postgres → ClickHouse Cloud, and Postgres → Postgres. This deprecation applies to the **destination** role only — BigQuery remains a supported **source**. See the [connector status matrix](#status) and the [deprecated connectors migration guide](docs/deprecated-connectors.md) for how to pin to a release or fork the relevant code.
+> **Mirror type deprecation notice:** CDC is the recommended and actively-maintained mirror type. The **Query Replication (QRep)** and **XMIN** mirror types are deprecated and no longer actively maintained; they remain fully functional, and no code is currently being removed.
+
+> **Connector deprecation notice:** The Snowflake, BigQuery, ElasticSearch, Kafka (including Confluent and Redpanda variants), Azure Event Hubs, Google Pub/Sub, and S3 **destination** connectors are deprecated and no longer actively maintained. They remain fully functional in the current and all prior releases, and no code is currently being removed. The actively-maintained paths going forward are Postgres → ClickHouse, Postgres → ClickHouse Cloud, and Postgres → Postgres. This deprecation applies to the **destination** role only — BigQuery remains a supported **source**. See the [connector status matrix](#status) and the [deprecated connectors migration guide](docs/deprecated-connectors.md) for how to pin to a release or fork the relevant code.
 
 ## Get started
 
@@ -67,7 +69,7 @@ PeerDB is an ETL/ELT tool built for PostgreSQL. We implement multiple Postgres n
 
 **For reliability**, we have mechanisms in place for fault tolerance - state management, automatic retries, handling idempotency and consistency and so on (<https://blog.peerdb.io/using-temporal-to-scale-data-synchronization-at-peerdb>). Configurable batching and parallelism prevent out of memory (OOMs) and crashes.
 
-**From a feature richness standpoint**, we support efficient syncing of tables with large (TOAST) columns. We support multiple streaming modes - log based (CDC), cursor based (timestamp or integer) and XMIN based. We provide rich data-type mapping and plan to support every possible type (incl. Custom types) that Postgres supports to the best extent possible on the target data-store.
+**From a feature richness standpoint**, we support efficient syncing of tables with large (TOAST) columns. We support multiple streaming modes - log based (CDC), cursor based (timestamp or integer) and XMIN based (the cursor-based / Query Replication and XMIN modes are deprecated; CDC is recommended). We provide rich data-type mapping and plan to support every possible type (incl. Custom types) that Postgres supports to the best extent possible on the target data-store.
 
 ### Now available natively in ClickHouse Cloud (Generally Available)
 

docs/deprecated-connectors.md

@@ -10,7 +10,7 @@ The following **destination** connectors are deprecated and no longer actively m
 - Google Pub/Sub
 - S3
 
-These connectors remain **fully functional** in the current and all prior releases. No code is being removed, and they will **not** be automatically removed from existing deployments. The actively-maintained paths going forward are Postgres → ClickHouse, Postgres → ClickHouse Cloud, and Postgres → Postgres. Sources (Postgres, MySQL, MongoDB) are not affected by this deprecation.
+These connectors remain **fully functional** in the current and all prior releases. No code is currently being removed, and they will **not** be automatically removed from existing deployments. The actively-maintained paths going forward are Postgres → ClickHouse, Postgres → ClickHouse Cloud, and Postgres → Postgres. Sources (Postgres, MySQL, MongoDB) are not affected by this deprecation.
 
 > **BigQuery is deprecated only as a destination.** BigQuery remains a **supported source** for QRep mirrors and is not deprecated in that role. The migration guidance below applies to BigQuery's use as a *destination*.
 
@@ -27,7 +27,7 @@ Pin to the latest release tag before any future removal so that you have the mos
 
 ## How to fork
 
-Because no code is being removed, you can fork PeerDB and carry the relevant connector code yourself. The connectors are self-contained enough that forking and maintaining a single connector is practical:
+Because the connector code is still present, you can fork PeerDB and carry the relevant connector code yourself. The connectors are self-contained enough that forking and maintaining a single connector is practical:
 
 1. Fork the repository.
 2. Keep the connector's flow code, its UI form and helper, and (optionally) its end-to-end tests so you can continue validating it.

ui/app/api/mirror-types/route.ts

@@ -15,13 +15,15 @@ export async function GET(_: NextRequest) {
       description:
         'Query Replication allows you to specify a set of rows to be synced via a SELECT query. Useful for replicating views and tables without primary keys.',
       link: 'https://docs.peerdb.io/usecases/Streaming%20Query%20Replication/overview',
+      deprecated: true,
     },
   ];
   const xminCard = {
     title: MirrorType.XMin,
     description:
       'XMIN mode uses the xmin system column of PostgreSQL as a watermark column for replication.',
     link: 'https://docs.peerdb.io/sql/commands/create-mirror#xmin-query-replication',
+    deprecated: true,
   };
 
   if (!GetPeerDBClickHouseMode()) {

ui/app/mirrors/create/mirrorcards.tsx

@@ -1,6 +1,7 @@
 'use client';
 import { MirrorType } from '@/app/dto/MirrorsDTO';
 import { fetcher } from '@/app/utils/swr';
+import { Badge } from '@/lib/Badge';
 import { Label } from '@/lib/Label';
 import { RowWithRadiobutton } from '@/lib/Layout';
 import { ProgressCircle } from '@/lib/ProgressCircle';
@@ -22,6 +23,7 @@ export default function MirrorCards({
       title: MirrorType;
       description: string;
       link: string;
+      deprecated?: boolean;
     }[]
   >('/api/mirror-types', fetcher);
 
@@ -50,7 +52,26 @@ export default function MirrorCards({
                 <RowWithRadiobutton
                   label={
                     <Label>
-                      <div style={{ fontWeight: 'bold' }}>{card.title}</div>
+                      <div
+                        style={{
+                          fontWeight: 'bold',
+                          display: 'flex',
+                          alignItems: 'center',
+                          gap: '0.5rem',
+                        }}
+                      >
+                        {card.title}
+                        {card.deprecated && (
+                          <Badge variant='destructive'>
+                            <Label
+                              as='label'
+                              style={{ fontSize: 13, padding: 0 }}
+                            >
+                              Deprecated
+                            </Label>
+                          </Badge>
+                        )}
+                      </div>
                     </Label>
                   }
                   action={<RadioButton value={card.title} />}