cascading delete, mcaptcha add/del and test suite

migrations/20210310122617_mcaptcha_config.sql

@@ -1,6 +1,7 @@
 CREATE TABLE IF NOT EXISTS mcaptcha_config (
 	config_id SERIAL PRIMARY KEY NOT NULL,
-	ID INTEGER references mcaptcha_users(ID),
+	domain_name VARCHAR(100) NOT NULL references mcaptcha_domains(name) ON DELETE CASCADE,
 	key VARCHAR(100) NOT NULL UNIQUE,
+	name VARCHAR(100) NOT NULL UNIQUE,
 	duration INTEGER NOT NULL DEFAULT 30
 );