Cross-database compatibility

Hey Team,

First off, thank you for this awesome project!

I'm currently working on a use case where it's "Bring Your Own DB" (BYODB) and was wondering what the types supported are? The first issue I hit with MySQL and Postgres was binary support for storing UUIDs.

My first reading of the docs _suggested_ that DBML sat at a higher level which led me to believe that would generate the specific types per-database output:

> DBML is database-agnostic and designed for the high-level database architecting instead of low-level database creation

AFAIK you've got two choices, `varchar(36)` or `binary(16)` (https://github.com/holistics/dbml/issues/544) at least in MySQL world, which should be either `uuid` or `bytea` in postgres.

Is there a way to work with different types across multiple database backends where types need to differ?

I would like my DBML to be the single source of truth 😄

## Related issues:
- https://github.com/holistics/dbml/issues/544

## Workarounds
- Use `varchar(36)`, which works across both DBs at the expense of being in-optimal in terms of storage.