Add CDB_Username() function

scripts-available/CDB_Username.sql

@@ -0,0 +1,13 @@
+-- Function returning the username of the provided user
+CREATE OR REPLACE FUNCTION _CDB_Username(pg_user TEXT)
+RETURNS text
+AS $$
+  SELECT CDB_Conf_GetConf(CONCAT('api_keys_', pg_user))->>'username';
+$$ LANGUAGE SQL STRICT IMMUTABLE PARALLEL SAFE SECURITY DEFINER;
+
+-- Function returning the username of the current user
+CREATE OR REPLACE FUNCTION CDB_Username()
+RETURNS text
+AS $$
+  SELECT _CDB_Username(current_user);
+$$ LANGUAGE SQL STABLE PARALLEL SAFE;