Due to issues with login on my single-user instance (mastodon.eroticmohel.com), I revoked the OAuth access token. In doing so, I believe this led to the deletion of the OAuth application on my server, and thus to the following issue.

It may also be worth mentioning that, until about two hours ago, I didn't have Access-Control-Allow-Origin: * set or Access-Control-Allow-Headers configured, which generally led to issues.

Steps to reproduce:

1. Log in to Elk.Zone on server (running Docker container yakumosaki/glitch-soc:20230923_17)
2. On the Mastodon server, revoke the authorized application
3. Back on Elk.Zone, attempt to log in once again

Expected behavior:
Successful login

Actual behavior:
Mastodon server issues the error "Client authentication failed due to unknown client, no client authentication included, or unsupported authentication method."

mastodon=# select * from oauth_applications where redirect_uri like '%elk.zone%';
 name | uid | secret | redirect_uri | scopes | created_at | updated_at | superapp | website | owner_type | id | owner_id | confidential
------+-----+--------+--------------+--------+------------+------------+----------+---------+------------+----+----------+--------------
(0 rows)

Potential solution:
Provide some way for users of Elk.Zone to have the server "forget" about their instance. As it stands, the OAuth client details stored for my instance are incorrect, and clearing those should fix this issue.