Add new record type partner.
This can be something like a media partner or something else.
Allow an event to have zero or more partner.
Add necessary files and models with relations.
Relates: #8092
Allow editor to reference TYPO3 page records from events.
E.g. used to provide further internal information links.
Also those pages are resolved via DataProcessing.
That allows integrators to be 100% flexible to resolve those page info.
By default a menu is generated and media is resolved.
Also validation is ignored, as this improves performance and allows to
use the new class as injected property without validation fails.
Models are not managed via frontend and therefore don't need validation.
Relates: #8092
