fix(IRegistrationContext): Add missing TaskProcessing methods

[provokateurin]

Summary

Follow up for #45094. The methods are present in the implementation but not in the interface, so the interface is not complete and also psalm complains about it.

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)

[marcelklehr]

Strange that the CI was green when I merged.

[provokateurin]

Well the server CI is fine because the method is never called here. Just trying to call it from app_api it complains because the method is missing on the interface.