fix(oauth2): adjust db schemas when migrating from owncloud

[st3iny]

• Resolves: [Bug]: The schema of oc_oauth2_access_tokens is not adjusted properly and its data is not migrated correctly when migrating from ownCloud #50186

Summary

See also #49075

This PR fixes two issues:

1. Not being able to create or auth using OAuth2 clients after migrating from ownCloud.
2. Not being able to refresh legacy tokens from ownCloud after migrating to Nextcloud.

It does not aim to migrate legacy access tokens from ownCloud as this incurs a lot of work and tokens are only valid for an hour. So, it does not make sense as the migration window set by admins is probably longer than their lifetime anyway.

What I tested

1. Install ownCloud (latest) and install/enable the oauth2 app.
2. Add an oauth2 client, use it to generate an access token and refresh it at least once.
3. Dump related tables: mysqldump owncloud oc_oauth2_access_tokens oc_oauth2_refresh_tokens oc_oauth2_clients
4. Import dumped tables into Nextcloud.
5. Reset all oauth2 migrations and drop oauth2 tables (oc_oauth2_access_tokens, oc_oauth2_refresh_tokens and oc_oauth2_clients).
6. Import dumped tables.
7. Migrate oauth2 and run repair steps: occ migrations:migrate oauth2 && occ maintenance:repair
8. Refresh the token generated in step 2 using your oauth2 client (might be necessary to adjust the token URL if Nextcloud is on another domain).
9. Observe that the refreshed access token can still be used to log into Nextcloud.

TODO

• Needs to be tested with a live ownCloud instance (see above)

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[ChristophWurst]

Looks good so far

[st3iny]

/backport! to stable29