TTW DX Layout disables IBlocks behavior and with it all the indexers and transformers

[avoinea]

Issue:

By enabling TTW DX Layout for content-types the volto.blocks behavior is removed in order to be able to edit blocks and blocks_layout defaults. The side effect of this is that also the IBlocks interface is removed from ctype / objects and with it all the registered IBlocks indexers, serializers, deserializers.

e.g.: https://github.com/plone/plone.restapi/blob/9f205c1b9514d09e45c855899a820b3c703d49f3/src/plone/restapi/serializer/blocks.py#L141-L143

Solution:

A new marker interface behavior for TTW DX layout blocks:

class IBlocksEditableLayout(IBlocks):
    """ Volto Blocks Editable Layout marker interface """