Refactor the Sentry plugin to use the proxy backend instead of a custom backend

.changeset/chatty-pens-bathe.md

@@ -0,0 +1,65 @@
+---
+'@backstage/plugin-sentry': minor
+'@backstage/plugin-sentry-backend': minor
+---
+
+The plugin uses the `proxy-backend` instead of a custom `sentry-backend`.
+It requires a proxy configuration:
+
+`app-config.yaml`:
+
+```yaml
+proxy:
+  '/sentry/api':
+    target: https://sentry.io/api/
+    allowedMethods: ['GET']
+    headers:
+      Authorization:
+        $env: SENTRY_TOKEN # export SENTRY_TOKEN="Bearer <your-sentry-token>"
+```
+
+The `MockApiBackend` is no longer configured by the `NODE_ENV` variable.
+Instead, the mock backend can be used with an api-override:
+
+`packages/app/src/apis.ts`:
+
+```ts
+import { createApiFactory } from '@backstage/core';
+import { MockSentryApi, sentryApiRef } from '@backstage/plugin-sentry';
+
+export const apis = [
+  // ...
+
+  createApiFactory(sentryApiRef, new MockSentryApi()),
+];
+```
+
+If you already use the Sentry backend, you must remove it from the backend:
+
+Delete `packages/backend/src/plugins/sentry.ts`.
+
+```diff
+# packages/backend/package.json
+
+...
+    "@backstage/plugin-scaffolder-backend": "^0.3.2",
+-   "@backstage/plugin-sentry-backend": "^0.1.3",
+    "@backstage/plugin-techdocs-backend": "^0.3.0",
+...
+```
+
+```diff
+// packages/backend/src/index.html
+
+  const apiRouter = Router();
+  apiRouter.use('/catalog', await catalog(catalogEnv));
+  apiRouter.use('/rollbar', await rollbar(rollbarEnv));
+  apiRouter.use('/scaffolder', await scaffolder(scaffolderEnv));
+- apiRouter.use('/sentry', await sentry(sentryEnv));
+  apiRouter.use('/auth', await auth(authEnv));
+  apiRouter.use('/techdocs', await techdocs(techdocsEnv));
+  apiRouter.use('/kubernetes', await kubernetes(kubernetesEnv));
+  apiRouter.use('/proxy', await proxy(proxyEnv));
+  apiRouter.use('/graphql', await graphql(graphqlEnv));
+  apiRouter.use(notFoundHandler());
+```