Add some functions

20230125142000_functions.down.sql

@@ -0,0 +1,4 @@
+BEGIN;
+DROP FUNCTION is_name;
+DROP FUNCTION is_language_code;
+COMMIT;

20230125142000_functions.up.sql

@@ -0,0 +1,16 @@
+BEGIN;
+
+CREATE FUNCTION is_name(value TEXT) RETURNS BOOLEAN LANGUAGE plpgsql AS $$
+BEGIN
+    RETURN value = btrim(value) AND length(value) > 0;
+END;
+$$;
+
+CREATE FUNCTION is_language_code(value VARCHAR) RETURNS BOOLEAN LANGUAGE plpgsql
+AS $$
+BEGIN
+    RETURN value ~ '^[a-z]{2}$';
+END;
+$$;
+
+COMMIT;