pg_cron: cron.database_name does not support multiple databases

[shameerBhupathi]

Environment:
PostgreSQL 15,16,17,18 with pg_cron extension
Multiple databases: db01, db02, postgres
Platform: AWS RDS / Linux in RHEL 9

Issue Description:
Attempting to create the pg_cron extension in the db02 database fails with a configuration error, even though cron.database_name has been set via ALTER SYSTEM.

Steps to Reproduce:

1. Run: ALTER SYSTEM SET cron.database_name = 'db01, db02,postgres';
2. In the db02 database, run: CREATE EXTENSION pg_cron;

Error Message:
db02=# create extension pg_cron;
ERROR: can only create extension in database db01, db02,postgres
DETAIL: Jobs must be scheduled from the database configured in cron.database_name, since the pg_cron background worker reads job descriptions from this database.
HINT: Add cron.database_name = 'db02' in postgresql.conf to use the current database.

Root Cause Analysis:
The error suggests that cron.database_name is being treated as a single database identifier rather than parsing the comma-separated list. The extension expects an exact match between the current database and the configured value, but instead receives the entire string 'db01, db02,postgres'.

Expected Behavior:
pg_cron should parse comma-separated database names and allow the extension to be created in any of the listed databases.