Create an Endpoint to cause a refresh of the PostgreSQL Database Connection Cache

Create an endpoint to trigger a PostgreSQL database connection cache refresh.

Currently, the only way to do this is to cause the ETP Server's pod to restart, which can disrupt customer connection.

Use cases for this change are to indicate to the ETP Server to check for additional partitions that now have the reservoir-connection parameter specified (for example, this could be called after bootstrapping the partition information to set the reservoir-connection).

This could also help with whenever the PostgreSQL main user's password is rotated as is recommended by security.