File that must contain the environment variable PGBOUNCER_EXPORTER_CONNECTION_STRING which is set to the connection string used by pgbouncer. I.e. the format is supposed to look like this:
PGBOUNCER_EXPORTER_CONNECTION_STRING="postgres://admin@localhost:6432/pgbouncer?sslmode=require"
NOTE: You MUST keep pgbouncer as database name (special internal db)! NOTE: services.pgbouncer.settings.pgbouncer.ignore_startup_parameters MUST contain "extra_float_digits".