Add aliasing to serializer formatting

API attribute names don't always match the database column names. This release adds the ability to specify separate api attribute and optional database attribute names.

ensure_zulu_time api_attribute, db_attribute

ensure_zulu_time enabled_at                # both are the same
ensure_zulu_time enabled_at, enabled_date  # API is enabled_at, DB is enabled_date

and this works similarly with enforce_iso8601_date