Log message:
postgresql15: added version 15.0

PostgreSQL 15 contains many new features and enhancements, including:

Support for the SQL MERGE command.

Selective publication of tables' contents within logical replication \ 
publications, through the ability to specify column lists and row filter \ 
conditions.

More options for compression, including support for Zstandard (zstd) \ 
compression. This includes support for performing compression on the server side \ 
during pg_basebackup.

Support for structured server log output using the JSON format.

Performance improvements, particularly for in-memory and on-disk sorting.