Emit `sa.Enum(...).with_variant(postgresql.ENUM(...))` instead of `postgresql.ENUM(...)`

[Et7f3]

Hello,

Thanks for your works.

I know the project is called alembic-postgresql-enum but from outside it seems to be quite generic and in theory could be applied with multiple backend once create_type is added for others dialect.

Main alembic dev suggest this coding style:
sqlalchemy/alembic#1347 (comment)

One advantage I see is that we don't seems locked with postgresql (in the case in the future I need to change to other db).

[pstrzelczak]

Lack of this functionality blocks me to use this plugin. Could you consider to implement it? Thanks!

[HarryLesnar24]

I tried to open same feature requirement, but it is already opened kindly fix the alembic autogenerates from sa.Enum to postgresql.ENUM.