Generating default UUID on PostgreSQL 13/14

[Nawrok]

Hi @lecousin,
Currently, the implemented PostgreSQL dialect supports the default creation of UUID v4 using the UUID_GENERATE_V4() function derived from the extension. PostgreSQL database as of version 13 supports native function for UUID generation - gen_random_uuid() (https://www.postgresql.org/docs/current/functions-uuid.html), so it is not required to install the above extension.

I would ask you to support the native function in the currently used dialect or completely create a new dialect under the latest versions of the database.