Add changesets

Signed-off-by: Andrew Shirley <andrew.shirley@sainsburys.co.uk>
Signed-off-by: blam <ben@blam.sh>

.changeset/good-hornets-hunt.md

@@ -0,0 +1,65 @@
+---
+'@backstage/plugin-jenkins': major
+---
+
+## Extract an entity-oriented Jenkins Backend
+
+Change the Jenkins plugin from talking directly with a single jenkins instance (via the proxy) to having a specific
+backend plugin which talks to the jenkins instances.
+
+Existing users of the Jenkins plugin will need to configure a jenkins backend instead of a proxy.
+Typically, this means creating a `src/plugins/jenkins.ts` file, adding a reference to it to `src/index.ts` and changing app-config.yaml
+
+### jenkins.ts
+
+```typescript
+import {
+  createRouter,
+  DefaultJenkinsInfoProvider,
+} from '@backstage/plugin-jenkins-backend';
+import { CatalogClient } from '@backstage/catalog-client';
+import { Router } from 'express';
+import { PluginEnvironment } from '../types';
+
+export default async function createPlugin({
+  logger,
+  config,
+  discovery,
+}: PluginEnvironment): Promise<Router> {
+  const catalogClient = new CatalogClient({ discoveryApi: discovery });
+
+  return await createRouter({
+    logger,
+    jenkinsInfoProvider: new DefaultJenkinsInfoProvider(catalogClient, config),
+  });
+}
+```
+
+### app-config.yaml
+
+For example
+
+```yaml
+proxy:
+  '/jenkins/api':
+    target: 'https://jenkins.example.com:8080' # your Jenkins URL
+    changeOrigin: true
+    headers:
+      Authorization: Basic ${JENKINS_BASIC_AUTH_HEADER}
+```
+
+Would become:
+
+```yaml
+jenkins:
+  baseUrl: https://jenkins.example.com:8080
+  username: backstage-bot
+  apiKey: ${JENKINS_PASSWORD}
+```
+
+## Change BuildWithStepsPage route
+
+The plugin originally provided a route to view a particular build of a particular branch so that if you wanted to view
+the master branch of an entity annotated with `'jenkins.io/github-folder': teamA/artistLookup-build` you could typically
+access `/catalog/default/component/artist-lookup/ci-cd/run/master/7` but would now have to access
+`/catalog/default/component/artist-lookup/ci-cd/build/teamA%2FartistLookup-build%2Fmaster/7`

.changeset/light-frogs-prove.md

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+---
+'example-backend': patch
+'@backstage/plugin-jenkins-backend': patch
+---
+
+## Extract an entity-oriented Jenkins Backend
+
+Change the Jenkins plugin from talking directly with a single jenkins instance (via the proxy) to having a specific
+backend plugin which talks to the jenkins instances.