refactor: improve roles.sql

Add back active_connections, smarter connection_limit.

Author: soedirgo

src/lib/sql/roles.sql

@@ -7,10 +7,30 @@ SELECT
   rolcanlogin AS can_login,
   rolreplication AS is_replication_role,
   rolbypassrls AS can_bypass_rls,
-  rolconnlimit AS connection_limit,
+  active_connections,
+  CASE WHEN rolconnlimit = -1 THEN max_db_connections :: int4
+       ELSE rolconnlimit
+  END AS connection_limit,
   rolpassword AS password,
   rolvaliduntil AS valid_until,
   rolconfig AS config,
-  oid
+  oid AS id
 FROM
   pg_catalog.pg_roles
+  INNER JOIN LATERAL (
+    SELECT
+      count(*) AS active_connections
+    FROM
+      pg_stat_activity
+    WHERE
+      state = 'active'
+      AND pg_roles.rolname = pg_stat_activity.usename
+  ) AS active_connections ON 1 = 1
+  INNER JOIN LATERAL (
+    SELECT
+      setting AS max_db_connections
+    FROM
+      pg_settings
+    WHERE
+      name = 'max_connections'
+  ) AS max_db_connections ON 1 = 1