docs: post fixes for oc11

[mmattel]

This PR provides some post fixes related to the OC11 docs.

• Several updates for missing envvars
• Updated texts in troubleshooting
• Removal Update of oidc configuration (needs mentioning in the release notes)

Note that memcached changes will be added as soon as the fixes are available. Keeping the PR as draft therefore.

[DeepDiver1975]

Review: docs post fixes for OC11

Thanks for this — the direction is right. Migrating the config examples from config.php snippets to the container OWNCLOUD_* env-var form matches how OC11 is deployed, and the OIDC section restructuring (demoting the per-IdP examples to === under a single == General Example Setup, and removing the now-obsolete "Save Settings in the Database" section) is a good cleanup.

My main concern is correctness of the new env-var snippets — several of the JSON examples are not valid JSON and would fail if an admin copy-pasted them. Since the whole value of this PR is copy-pasteable configuration, these are worth fixing before merge. Details inline.

Must fix (broken markup / invalid examples)

• envvars.adoc — CUSTOMGROUPS_DISALLOWED_GROUPS xref has a misplaced ); OPENID_CONNECT xref is missing the xref: prefix.
• login_policies.adoc — both the template and the example JSON have syntax errors ("allowOnly|reject" as a key, unquoted keys, unescaped backslashes in the OIDC class name, a missing quote, a stray quote).
• user_auth_ftp_smb_imap.adoc — typo opwnCloud.
• general_troubleshooting.adoc — grammar "problems raise" → "arise".

Please confirm (uncertain — flagging rather than assuming)

• Value formats. This PR introduces three different multi-value encodings: JSON arrays (USER_BACKENDS, MEMCACHED_SERVERS), quoted CSV (CUSTOMGROUPS_DISALLOWED_GROUPS), and the login-policy JSON map. Can you confirm each matches exactly what the container entrypoint parses? A wrong format here is worse than the old config.php docs because it looks authoritative.
• Multi-line .env values. The login-policy example uses trailing \ line continuations inside a [source,.env] block — does the entrypoint actually accept that?
• Troubleshooting content removal. The Windows WebDAV 0x80070043 Apache workaround and the CalDAV/CardDAV service-discovery guidance are being replaced with "open an issue." That's still-valid, non-OC11-specific admin content — is removing it (vs. updating it) intentional?

Nits

• xref anchor #define-the-user_backends-app — verify it resolves given the backtick-formatted target heading.
• caching_configuration.adoc — a one-line note on what weight means would help.

No test coverage concerns (docs-only). Overall a solid update once the invalid snippets are corrected.

[DeepDiver1975]

The xref target #define-the-user_backends-app — the heading in config_sample_php_parameters.adoc is === Define the \user_backends` app. With the backtick-wrapped user_backends, Antora's auto-generated ID may not be define-the-user_backends-app(backticks/formatting can affect the generated anchor). Please verify this resolves during a build, or add an explicit[#define-the-user_backends-app]` anchor on the target heading.

[mmattel]

Resolves correctly

[DeepDiver1975]

Format consistency: this example uses OWNCLOUD_CUSTOMGROUPS_DISALLOWED_GROUPS='no_guest_app_users','project5' (single-quoted, comma-separated), while the corresponding envvars.adoc entry describes it as a plain "comma-separated list of group names" and the other new multi-value envvars in this PR use JSON arrays. Can you confirm the container actually expects this quoted-CSV form (and not e.g. no_guest_app_users,project5 or a JSON array)? The three formats introduced across this PR (JSON arrays, quoted CSV, plain CSV) should each match what the entrypoint parses.

[mmattel]

Intentionally, a reminder to the admin to avoid parsing special characters wrong

There are also syntax errors to be fixed.