When Postgres is used as the backing database for headscale,
it does not set a limit on maximum open and idle connections
which leads to hundreds of open connections to the Postgres
server.
This commit introduces the configuration variables to set those
values and also sets default while opening a new postgres connection.
There was a lot of tests that actually threw a lot of errors and that did
not pass all the way because we didnt check everything. This commit should
fix all of these cases.
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
