Allow specifying a schema for created databases

[James Westby]

When creating a db you usually want to populate it with a schema so you can start running queries.

It might be nice for postgresfixture to allow specifying a schema and it doing the work of
executing the DDL.

Thanks,

James

[Gavin Panella (allenap)]

As discussed on IRC, I think postgresfixture's lack of features is a virtue right now, but if this can be done "to one side", say as a subclass of ClusterFixture, or as a fixture that accepts a Cluster, that would fit in nicely.

[Robert Collins (lifeless)]

FWIW there is schema application code in lazr.postgresql, which would
be most suitable for combining with this, vs conflating schema
management and cluster management.

[Gavin Panella (allenap)]

Thanks for that Rob. I suspect fixing this bug will involve documenting some options rather than adding code.