[multi-sources-removal] Drop entities.source column
Since we remove federated multi-sources support, the same value ('system')
is always stored in this column and so could be removed. Also, cleanup
repository caches and a few api where the very same useless information could
be removed.
Closes #2919300, at last
[jcr: restore sanity check of etype against schema in checkintegrity.has_eid]
from cubicweb.schemas.base import in_group, CWSourceSchemaConfig
# copy __permissions__ to avoid modifying a shared dictionary
in_group.__permissions__ = in_group.__permissions__.copy()
in_group.__permissions__['read'] = ('managers',)
cw_for_source = CWSourceSchemaConfig.get_relation('cw_for_source')
cw_for_source.__permissions__ = {'read': ('managers', 'users'),
'add': ('managers',),
'delete': ('managers',)}