[FEATURE] Add MigrateFlexFormParsingHooksToEventListenersRector

[kitzberger]

Migrates FlexForm parsing hooks to PSR-14 event listeners:

• parseDataStructureByIdentifierPreProcess -> BeforeFlexFormDataStructureParsedEvent
• parseDataStructureByIdentifierPostProcess -> AfterFlexFormDataStructureParsedEvent
• getDataStructureIdentifierPreProcess -> BeforeFlexFormDataStructureIdentifierInitializedEvent
• getDataStructureIdentifierPostProcess -> AfterFlexFormDataStructureIdentifierInitializedEvent

See https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/12.0/Feature-97449-PSR-14EventsForModifyingFlexFormParsing.html

[simonschaufi]

There is a reason why we don't have any hooks to Event listener migration because it is just way too complex. I don't see this rule as a rule that fully migrates everything but more like a "the code is half migrated" rule and you still need to make your hands dirty.

I'm not sure if I should accept such "broken" rules that only migrate half of the code. The only thing I can imagine is to move the new folder for "half migrations" (similar like code quality). Then I would put that into an own rule set and activate it only as a helper set but I would never put that into a full TYPO3 version set.

Specifically for this migration: The namespace must also be adjusted which I would expect to be correct at least.

What do you think?

[kitzberger]

That's what I was wondering too. For me as a user of rector it would be super helpful to be pushed into the right direction when running the full set migrations. basically like this: look at this old piece of code, it needs to be changed from this hook to an eventlistener, we've kickstarted a skeleton class for you, but now you need to do some thinking of your own, mate.

[simonschaufi]

For me it is important that all the rules under the TYPO3 namespace are stable and don't produce half broken code. That event listener is currently not working.