add blog on how to use starlark in Woodpecker CI

Signed-off-by: prashant-gurung899 <prasantgrg777@gmail.com>

Author: prashant-gurung899

src/assets/woodpeckerCI/woodpeckerCI.md

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+---
+title: Starlark in woodpecker CI
+authorName: Prashant Gurung
+authorAvatar: https://avatars.githubusercontent.com/u/53248463?v=4
+authorLink: https://github.com/prashant-gurung899
+createdAt: July 3, 2025
+tags: CI/CD
+banner: https://raw.githubusercontent.com/JankariTech/blog/master/src/imgs/fallback_banner.png
+---
+
+## Background
+Continuous Integration (CI) tools are vital for automating the testing and deployment of modern software. One such open-source tool is Woodpecker CI, a lightweight CI/CD system. Traditionally, Woodpecker pipelines are written in YAML. But with the rise of programmable pipelines, we now have the flexibility to define our CI configuration using Starlark — a Python-like configuration language.
+
+In this blog, I’ll walk you through how I set up Woodpecker CI with a dynamic Starlark-to-YAML conversion service (WCCS), enabling us to write pipelines in .drone.star files. Here's a high-level view of what we'll cover:
+
+- Spinning up a Woodpecker server
+
+- Authenticating with GitHub
+
+- Enabling a repository
+
+- Setting up WCCS (Woodpecker Config Conversion Service)
+
+- Connecting WCCS with the Woodpecker server
+
+By the end, you’ll be able to write CI pipelines in Starlark and dynamically convert them to YAML during runtime.
+
+
+## Setting Up Woodpecker Server
+We started by running the Woodpecker server using Docker. Here's the essential setup:
+
+```yml
+version: '3'
+services:
+  woodpecker-server:
+    image: woodpeckerci/woodpecker-server:latest
+    ports:
+      - 8000:8000
+    environment:
+      - WOODPECKER_OPEN=true
+      - WOODPECKER_HOST=https://<ngrok-or-your-domain>
+      - WOODPECKER_GITHUB=true
+      - WOODPECKER_GITHUB_CLIENT=<client-id>
+      - WOODPECKER_GITHUB_SECRET=<client-secret>
+      - WOODPECKER_AGENT_SECRET=supersecret
+      - WOODPECKER_CONFIG_ENDPOINT=http://wccs:3000/ciconfig
+    volumes:
+      - woodpecker-data:/var/lib/woodpecker
+
+  woodpecker-agent:
+    image: woodpeckerci/woodpecker-agent:latest
+    depends_on:
+      - woodpecker-server
+    environment:
+      - WOODPECKER_SERVER=http://woodpecker-server:8000
+      - WOODPECKER_AGENT_SECRET=supersecret
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+
+volumes:
+  woodpecker-data:
+```
+
+## Authenticating with GitHub
+
+To connect GitHub with Woodpecker:
+
+1. Register a new OAuth application in your GitHub developer settings.
+
+2. Set the callback URL to https://<your-ngrok-url>/authorize
+
+3. Copy the generated Client ID and Secret.
+
+4. Use these values in the WOODPECKER_GITHUB_CLIENT and WOODPECKER_GITHUB_SECRET env vars.
+
+After that, you can log into the Woodpecker web UI using your GitHub account.
+
+## Enabling a Repository
+From the Woodpecker UI:
+
+- Select your GitHub repo.
+
+- Enable it for CI.
+
+Woodpecker will automatically add the necessary webhooks to the repo.
+
+## Setting Up WCCS-Woodpecker CI Config Service (Starlark Conversion Service)
+WCCS is a small web service that receives a signed POST request from Woodpecker and returns a valid YAML pipeline. We deployed it with Docker:
+```yml
+wccs:
+  image: opencloudeu/wccs:latest
+  ports:
+    - 3000:3000
+  command: server
+```
+
+## Generating the Public Key
+We started the Woodpecker server first, let it generate a key pair, and then copied the public key from the container or volume path:
+```console
+docker cp woodpecker-server:/var/lib/woodpecker/keys/public.pem ./woodpecker.pub
+```
+
+## Connecting WCCS with Woodpecker
+To allow Woodpecker to fetch pipeline configs from WCCS, we added this to the server env:
+```console
+WOODPECKER_CONFIG_ENDPOINT=http://wccs:3000/ciconfig
+```
+Woodpecker now sends a signed JSON payload to WCCS whenever a build is triggered. WCCS verifies the signature using the public key and responds with a YAML pipeline based on your .woodpecker.star file.
+
+## Testing WCCS Manually
+
+To debug or test WCCS manually, we used curl:
+```console
+curl -v -X POST http://localhost:3000/ciconfig \
+  -H "Content-Type: application/json" \
+  -d '{"repo": {"name": "demo"}, "build": {"event": "push", "branch": "main"}}'
+```
+
+## Sample Starlark Pipeline
+Here's a simple .woodpecker.star example:
+```console
+def main(ctx):
+    return {
+        "steps": [
+            {
+                "name": "hello",
+                "image": "alpine",
+                "commands": ["echo Hello from Starlark"]
+            }
+        ]
+    }
+```
+This gets converted by WCCS into a valid Woodpecker pipeline YAML.
+
+Now, we can write pipelines in Starlark and let WCCS handle the conversion on the fly. This approach brings flexibility, structure, and the power of logic-based configurations to our CI pipelines.
+
+Want to try it yourself? Check out Woodpecker's config service example and start building smarter pipelines today!