Mark serial types as optional

[ration]

Hi,

I attempted to use the generated schemas in knex to insert rows, but ran into an (obvious?) issue that the interface for the rows require the primary key, which of course I don't yet have. Does this make sense for schemats?

Can I work around this somehow?

Just to fiddle with the idea I made a POC for PostgreSQL that does this: https://github.com/ration/schemats/tree/optional_serial