Typescript: safer nullability in functions, domain support

[ngasull]

What kind of change does this PR introduce?

Fixes #842

What is the current behavior?

CREATE DOMAIN strict_text AS text NOT NULL;

CREATE FUNCTION some_function(arg strict_text)
RETURNS table (nulltext text, stricttext strict_text)
LANGUAGE SQL AS $$
   SELECT NULL::text, arg
$$;

Generated type with supabase gen types typescript --local

export interface Database {
  public: {
    Functions: {
      some_function: {
        Args: {
          arg: unknown
        }
        Returns: {
          nulltext: string
          stricttext: unknown
        }[]
      }
    }
  }
}

What is the new behavior?

Generated types should be:

export interface Database {
  public: {
    Functions: {
      some_function: {
        Args: {
          arg: string
        }
        Returns: {
          nulltext: string | null
          stricttext: string
        }[]
      }
    }
  }
}

Please review tests for more details on new expected behavior.

• Stop accepting non-nullable types in generated function arguments and return types.
• Add support for domains and take their nullability into account.
• Centralize nullability and array logic in pgTypeToTsType.

Additional context

This is obviously a breaking change for most users using functions. It is however the safe way, exposing sound types.