## Problem
When client specifies `application_name`, pgbouncer propagates it to the
Postgres. Yet, if client doesn't do it, we have hard time figuring out
who opens a lot of Postgres connections (including the `cloud_admin`
ones).
See this investigation as an example:
https://neondb.slack.com/archives/C0836R0RZ0D
## Summary of changes
I haven't found this documented, but it looks like pgbouncer accepts
standard Postgres connstring parameters in the connstring in the
`[databases]` section, so put the default `application_name=pgbouncer`
there. That way, we will always see who opens Postgres connections. I
did tests, and if client specifies a `application_name`, pgbouncer
overrides this default, so it only works if it's not specified or set to
blank `&application_name=` in the connection string.
This is the last place we could potentially open some Postgres
connections without `application_name`. Everything else should be either
of two:
1. Direct client connections without `application_name`, but these
should be strictly non-`cloud_admin` ones
2. Some ad-hoc internal connections, so if we see spikes of unidentified
`cloud_admin` connections, we will need to investigate it again.
Fixesneondatabase/cloud#20948
Instead of adding them to the VM image late in the build process, when
putting together the final VM image, include them in the earlier
compute image already. That makes it more convenient to edit the
files, and to test them.
