feat(6222): remove @ and project from OIDC client ID (#8178)

# Which Problems Are Solved

The client ID for OIDC applications has an `@` in it, which is not
allowed in some 3rd-party systems (such as AWS).

# How the Problems Are Solved

Per @fforootd and @hifabienne in #6222, remove the project suffix and
the `@` from the client ID and just use the generated ID.

# Additional Changes

N/A

# Additional Context

- Closes #6222

---------

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>
Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/query/testdata/oidc_client_public.json

@@ -2,7 +2,7 @@
   "instance_id": "230690539048009730",
   "app_id": "236646457053020162",
   "state": 1,
-  "client_id": "236646457053085698@tests",
+  "client_id": "236646457053085698",
   "client_secret": null,
   "redirect_uris": ["http://localhost:9999/auth/callback"],
   "response_types": [0],