Add DATABASE_MAX_CONNS config setting

[rfwatson]

Tiny change to allow the database connection pool size to be configured externally (useful for those of us deploying to databases with limited connection count allowances)

[rfwatson]

Just spotted that this is a duplicate of #949 - feel free to close this one.

[PrivatePuffin]

This one is actually passing the checks and the other one isn't ;)

[whyvra]

Would love to see this PR merged in. When I tried to deploy bitwarden_rs today, it filled up all of my pgpool connections. I find it kinda crazy that it needs 10 simultaneous connections to the database.

+1

[BlackDex]

this PR has some conflicts so a simple merge is not possible.

[rfwatson]

I’ll fix the conflicts later if I have time

[BlackDex]

Well, there arn't any conflicts it seems.

But i do have one remark. It would be best if there is some validation done on the input value.
r2d2 states that if the value is 0 it will panic. I would like to prevent that from happening at all.

So i think at least a check that is is 1 or higher, maybe even a max, because i wouldn't want to have 1000 connections to my database by accident.

[rfwatson]

Updated in b9daa59

[BlackDex]

LGTM, and since there seems to be quite some request about this i think it is fine by me.