Merge pull request #13855 from OpenSourceZombie/ahmed/fix-ouath

gitlab oauth: consider hosted gitlab with relative path

.changeset/slow-mirrors-eat.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-auth-backend': patch
+---
+
+Fix GitLab provider setup so that it supports GitLab installations with a path in the URL.

plugins/auth-backend/src/providers/gitlab/provider.ts

@@ -91,6 +91,9 @@ export class GitlabAuthProvider implements OAuthHandlers {
         clientSecret: options.clientSecret,
         callbackURL: options.callbackUrl,
         baseURL: options.baseUrl,
+        authorizationURL: `${options.baseUrl}/oauth/authorize`,
+        tokenURL: `${options.baseUrl}/oauth/token`,
+        profileURL: `${options.baseUrl}/api/v4/user`,
       },
       (
         accessToken: any,