Add GitLab integration for scaffolder

This adds a GitLab integration for the scaffolder backend.

We're introduceing a preparer and a publisher for GitLab so that we can
read templates from GitLab and publish them to a configured GitLab
instance. The two instances don't need to be the same. For instance,
templates could be public on gitlab.com, but the created repos will live
in a hosted GitLab somewhere else.

The publisher gets its own config object in `app-config.yaml` where the
target instance and token can be specified.

The service catalogue defines both `gitlab` and `gitlab/api` as
processors. They are both handled by the same preparer.

Closes #2372

packages/backend/package.json

@@ -31,6 +31,7 @@
     "@backstage/plugin-scaffolder-backend": "^0.1.1-alpha.21",
     "@backstage/plugin-sentry-backend": "^0.1.1-alpha.21",
     "@backstage/plugin-techdocs-backend": "^0.1.1-alpha.21",
+    "@gitbeaker/node": "^23.5.0",
     "@octokit/rest": "^18.0.0",
     "dockerode": "^3.2.0",
     "example-app": "^0.1.1-alpha.21",

packages/backend/src/plugins/scaffolder.ts

@@ -19,13 +19,17 @@ import {
   createRouter,
   FilePreparer,
   GithubPreparer,
+  GitlabPreparer,
   Preparers,
+  Publishers,
   GithubPublisher,
+  GitlabPublisher,
   CreateReactAppTemplater,
   Templaters,
   RepoVisilityOptions,
 } from '@backstage/plugin-scaffolder-backend';
 import { Octokit } from '@octokit/rest';
+import { Gitlab } from '@gitbeaker/node';
 import type { PluginEnvironment } from '../types';
 import Docker from 'dockerode';
 
@@ -41,10 +45,15 @@ export default async function createPlugin({
 
   const filePreparer = new FilePreparer();
   const githubPreparer = new GithubPreparer();
+  const gitlabPreparer = new GitlabPreparer(config);
   const preparers = new Preparers();
 
   preparers.register('file', filePreparer);
   preparers.register('github', githubPreparer);
+  preparers.register('gitlab', gitlabPreparer);
+  preparers.register('gitlab/api', gitlabPreparer);
+
+  const publishers = new Publishers();
 
   const githubToken = config.getString('scaffolder.github.token');
   const repoVisibility = config.getString(
@@ -52,17 +61,32 @@ export default async function createPlugin({
   ) as RepoVisilityOptions;
 
   const githubClient = new Octokit({ auth: githubToken });
-  const publisher = new GithubPublisher({
+  const githubPublisher = new GithubPublisher({
     client: githubClient,
     token: githubToken,
     repoVisibility,
   });
+  publishers.register('file', githubPublisher);
+  publishers.register('github', githubPublisher);
+
+  const gitLabConfig = config.getOptionalConfig('scaffolder.gitlab.api');
+
+  if (gitLabConfig) {
+    const gitLabToken = gitLabConfig.getString('token');
+    const gitLabClient = new Gitlab({
+      host: gitLabConfig.getOptionalString('baseUrl'),
+      token: gitLabToken,
+    });
+    const gitLabPublisher = new GitlabPublisher(gitLabClient, gitLabToken);
+    publishers.register('gitlab', gitLabPublisher);
+    publishers.register('gitlab/api', gitLabPublisher);
+  }
 
   const dockerClient = new Docker();
   return await createRouter({
     preparers,
     templaters,
-    publisher,
+    publishers,
     logger,
     dockerClient,
   });