processor/drain: promote to alpha stability (#47763)

#### Description

Promote the Drain Processor from `development` to `alpha` stability and
add it to the `contrib` distribution.

Changes:
- Update `metadata.yaml`: `development` → `alpha`, `distributions:
[contrib]`
- Add to `cmd/otelcontribcol/builder-config.yaml`
- Add to `reports/distributions/contrib.yaml`
- Regenerate status and README via `mdatagen`
- Add changelog entry

#### Link to tracking issue
Fixes #47235

#### Testing

Existing tests pass. `make lint` and `go test -race ./...` clean in
`processor/drainprocessor/`.

#### Documentation

README auto-updated by `mdatagen` to reflect alpha stability and contrib
distribution.

Author: MikeGoldsmith

.chloggen/drain-processor-alpha.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: processor/drain
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Promote Drain Processor from development to alpha stability and add to contrib distribution.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [47235]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

cmd/otelcontribcol/builder-config.yaml

@@ -119,6 +119,7 @@ processors:
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/coralogixprocessor v0.150.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/deltatocumulativeprocessor v0.150.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/deltatorateprocessor v0.150.0
+  - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/drainprocessor v0.150.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/filterprocessor v0.150.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/geoipprocessor v0.150.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/processor/groupbyattrsprocessor v0.150.0

processor/drainprocessor/README.md

@@ -5,13 +5,14 @@ The Drain Processor applies the Drain log clustering algorithm to log records as
 
 | Status        |           |
 | ------------- |-----------|
-| Stability     | [development]: logs   |
-| Distributions | [] |
+| Stability     | [alpha]: logs   |
+| Distributions | [contrib] |
 | Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Aprocessor%2Fdrain%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aprocessor%2Fdrain) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Aprocessor%2Fdrain%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Aprocessor%2Fdrain) |
 | Code coverage | [![codecov](https://codecov.io/github/open-telemetry/opentelemetry-collector-contrib/graph/main/badge.svg?component=processor_drain)](https://app.codecov.io/gh/open-telemetry/opentelemetry-collector-contrib/tree/main/?components%5B0%5D=processor_drain&displayType=list) |
 | [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@MikeGoldsmith](https://www.github.com/MikeGoldsmith), [@atoulme](https://www.github.com/atoulme), [@martinjt](https://www.github.com/martinjt) |
 
-[development]: https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/component-stability.md#development
+[alpha]: https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/component-stability.md#alpha
+[contrib]: https://github.com/open-telemetry/opentelemetry-collector-releases/tree/main/distributions/otelcol-contrib
 <!-- end autogenerated section -->
 
 This processor **annotates**; it does not filter. Use the [filter processor](../filterprocessor/README.md) downstream to act on the `log.record.template` attribute — for example, to drop entire classes of noisy logs by pattern.

processor/drainprocessor/internal/metadata/generated_status.go

@@ -5,8 +5,8 @@ description: The Drain Processor applies the Drain log clustering algorithm to l
 status:
   class: processor
   stability:
-    development: [logs]
-  distributions: []
+    alpha: [logs]
+  distributions: [contrib]
   codeowners:
     active: [MikeGoldsmith, atoulme, martinjt]
 

processor/drainprocessor/metadata.yaml

@@ -104,6 +104,7 @@ components:
         - cumulativetodelta
         - deltatocumulative
         - deltatorate
+        - drain
         - filter
         - geoip
         - groupbyattrs