Move invite-accepted capability and implementation to contacts app.

[redblom]

• Resolves: #

Summary

Code moved to contacts app, see nextcloud/contacts#4417

TODO

• deal with inviteAcceptedDialog code

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)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[ChristophWurst]

@redblom why is this moved out of server and could it break OCM when the contacts app is not installed? the app is not shipped. it is optional.

[ArtificialOwl]

@redblom why is this moved out of server and could it break OCM when the contacts app is not installed? the app is not shipped. it is optional.

This is done on my request:

• it is moved out of server because the implementation of the feature creates its own db table and does not provide an API to manage it,
• it will not break OCM, it will only not enable the 'invite-accepted' capability if contacts is not installed. the capability is useless without the contacts app,
• contacts will register the capability and fully manage the db table

[ArtificialOwl]

let's ping @mickenordin on this one !

[mickenordin]

let's ping @mickenordin on this one !

I haven't reviewed the change, but in principal I see no problem with it.