[server] commit after serializing schema Use separate transactions for schema serialization and postcreate scripts execution, so that the latter can rely on the schema being persistently stored. This matters e.g. if something in a postcreate violates a unique_together constraint, we need the constraint persisted in order to raise a meaningful error. See #4525069.

[book] fix docstrings to please sphinx example rst roles in docstring must be protected (in a literal).

[book] several fixes in the rst files - prevent duplicate markup definitions, - use existing Workflow markup instead of redefining one (in baseschema.rst) - include dataimport - fix non-existant directive autodocfunction - remove the empty 'embedding.rst' file