Replace query to FAS with OIDC groups scope check.

This removes our query to FAS and fixes #304.

It is more flexible too, where we can now configure production to only
allow in members of the `modularity-wg` group, and then later open it up
to all packagers after F26 is out (as was agreed with FESCo).

In the process of working on this, I discovered that #305 is not
necessary.  We don't need our own scope; we can just use the `groups`
scope as done here.

.gitignore

@@ -11,3 +11,4 @@ test_module_build_service.db
 .mbs_local_build.db
 *.src.rpm
 .test_module_build_service.db
+.eggs