feat: add schema to /extensions

Author: soedirgo

src/lib/sql/extensions.sql

@@ -1,7 +1,9 @@
 SELECT
-  name,
-  comment,
-  default_version,
-  installed_version
+  e.name,
+  x.extnamespace :: regnamespace AS schema,
+  e.default_version,
+  x.extversion AS installed_version,
+  e.comment
 FROM
-  pg_available_extensions
+  pg_available_extensions() e(name, default_version, comment)
+  LEFT JOIN pg_extension x ON e.name = x.extname