When monitoring PostgreSQL with Zabbix agent 2 - one connection per each discovered DB is created

Steps to reproduce:

1. Install a PostgreSQL cluster (tested on version 13.5)
2. Create some DBs (can be empty)
3. Set the PostgreSQL cluster to be monitored via Zabbix agent 2 according to the official guide https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/templates/db/postgresql_agent2?at=release/5.0
4. Wait for the "Database discovery" discovery rule to run or run it explicitly
5. Watch the number of connections created by the "zbx_monitor" per each existing database

Result:

Expected:
One connection to the PostgreSQL cluster for all "zbx_monitoring" need.