Please document the list of functions added by the operator in the PostgreSQL DB.

Hi, while testing the charm, I discovered that there are a couple of functions that were added by the charm in the DB. In our case, this caused some issues as some of our custom database managment scripts were interferring with the permissions of these DPE related functions leading to weird issues.

It would be great if we can document all the functions in the "public" schema & other PG schemas that are created by the charm so that the users are aware of them and handle them explicitly if needed.

Here is the list of all the functions along with their schemas that I have found.

```
login_hook.get_login_hook_version() = EXECUTE
login_hook.is_executing_login_hook() = EXECUTE
login_hook.login() = EXECUTE
pgbouncer_auth_relation_6.get_auth(text) = EXECUTE
public.reset_user() = EXECUTE
public.reset_user(text) = EXECUTE
public.set_session_auth(text) = EXECUTE
public.set_up_predefined_catalog_roles() = EXECUTE
public.set_user(text) = EXECUTE
public.set_user_u(text) = EXECUTE
public.update_database_stats() = EXECUTE
public.update_replication_lag_cache() = EXECUTE
```

No documentation file or test is named. Start by checking the listed functions against the charm's PostgreSQL schemas and permissions, then locate the project's existing documentation entry point. Done means the charm-created functions and their schemas are documented so users can account for them in database management scripts.

Written by the indexing model from the issue text.