The implementation of the TYPO3 RequestFactory and Uri classes is
internal API.
It is therefore better to decorate the PSR-17 interfaces instead
of extending or using the TYPO3 implementation directly.
Provide first basic import mechanism.
It already allows to import entities into TYPO3 database.
Three entities are supported.
Entities are configured through import configuration.
This can be created, viewed, and edited through backend module.
Imports are tracked and accessible from backend module.
Still this is basic.
Importing lists of entities is not supported.
Multiple languages is not supported, etc.
Relates: #8214
