feat: AWS DSQL Support

[rcollette]

I noticed that there is a UseRedshift() method to align with that flavor of PostgreSQL. I've been encountering numerous issues with trying to run on AWS DSQL. Transaction isolation mode doesn't support read committed. Table locks are not supported. Discard is not supported.

It would be great if there was a UseDsql() method that used appropriate behaviors, particularly when running Migrations.

Thanks for considering.

[roji]

I'll put this in the backlog, but it's unlikely I'll get around to doing the work on it; for one thing, I don't have access to AWS DSQL or any knowledge on what it supports and what it doesn't.

Some of this is also likely to require changes in the lower-level Npgsql driver (e.g. not sending DISCARD). I'd start there, making Npgsql itself compatible, and then tackle things at the higher level of the EF provider.

If someone is willing to take this on, I'm happy to provide guidance.

[andrewbabbittdev]

Probably a good starting point would be drawing out and documenting all of the differences & incompatibilities before starting work so it can be scooped out.