[migration] drop identity_relation if it exists
It has been generated erroneously for a while, then fixed but not properly deleted from old
databases.
Don't use IF EXISTS for sqlserver compat.
.. -*- coding: utf-8 -*-
Writing text reports with RestructuredText
==========================================
|cubicweb| offers several text formats for the RichString type used in schemas,
including restructuredtext.
Three additional restructuredtext roles are defined by |cubicweb|:
.. autofunction:: cubicweb.ext.rest.eid_reference_role
.. autofunction:: cubicweb.ext.rest.rql_role
.. autofunction:: cubicweb.ext.rest.bookmark_role