feat: add pool-level sync_server_parameters override

[kontik-pk]

Summary

Add pool-level sync_server_parameters override

Problem

sync_server_parameters was a global-only setting in [general]. When enabled, client-sent session parameters (e.g. search_path, work_mem) are applied via SET queries on checkout. When disabled, they are silently ignored.

Solution

Added sync_server_parameters: Option to the [pools.] config section. When set, it overrides the global [general] value for that specific pool. When omitted, falls back to the global setting — preserving backward compatibility.

Backward compatibility

Fully compatible. Existing configs without sync_server_parameters on pool level continue to work exactly as before.

Config example

[general]
sync_server_parameters = false  # global default

[pools.some_db]
sync_server_parameters = true   # override for this pool