Feat/improve UUID varchar dataypes

[jackbravo]

This PR fixes two issues I've found:

1. VARCHAR types can be written without length parameter, essentially they can be an alias to TEXT.
2. make UUID types use a count generator with 32 hexadecimal characters. That way they can have an unique index which using a pattern (chars generators) didn't allow.

Example table with both errors:

create table app_public.projects (
  id                  uuid primary key default gen_random_uuid(),
  name                varchar not null
)