Story #69712: Further FormEngine development
Flex: Move TCA migration to data provider
This is @todo FlexFormElementContainer ~lines 100-130:
With 7, we're doing some changes to TCA. There is migration to move certain "old" cases not "new" definition. Those are handled early in bootstrap right after TCA was loaded in class TcaMigration. For flex forms however, this can not be done within bootstrap, but only if the TCA was parsed and extracted.
Task is to move the 'on the fly migration' done in FlexFormElemenContainer to TcaFlex provider to have this data preparation not in the render part anymore.