Add settings.plugins.mentions missing schema

kksandr → closed merge request !18

I fixed the schema issues and removed unused keys in the schema.

I also fixed other tests that did not pass, this is out of scope, so if this is a problem I can remove it.

I can't save Text Format configuration forms in the admin UI in Drupal 10.3 with this module enabled. Changing the schema from config_object to mapping (as this MR did) seemed to fix the problem.

I don't think I understand why this MR wasn't merged?

There are two different MRs. which to use?

MR22 no longer applies to new dev.

The schema bug should be fixed in the latest dev. I keep this ticket open because we need to remove not existing options from config schema e.g.

    use_advanced_pattern:
      type: boolean
      label: 'Use advanced pattern?'
    pattern:
      type: string
      label: 'Pattern'
    advanced_pattern:
      type: string
      label: 'Advanced pattern'

Does that take an update hook in addition to removing them in config?

I didn't test it but from my understanding after updating to CKEditor5 obsolete options are removed automatically, someone needs to check it out.