Add mysql to MESSAGE_QUEUE, KV_STORE, and DB_TO_CHECK in @fedify/init

Without this, the mysql entries in mq.json and kv.json were silently
ignored because the MessageQueue and KvStore types are derived from
the MESSAGE_QUEUE and KV_STORE constant arrays respectively, and mysql
was not listed in either.  As a result, fedify init never offered
MySQL/MariaDB as a selectable backend option despite the JSON entries
being present.

Also added mysql to DB_TO_CHECK and the corresponding db-to-check.json
so that the test suite can check whether a MySQL instance is running
before running integration tests.

#600 (comment)

Author: dahlia

packages/init/src/const.ts

@@ -12,13 +12,19 @@ export const WEB_FRAMEWORK = [
 ] as const;
 
 /** All supported message queue backend identifiers. */
-export const MESSAGE_QUEUE = ["denokv", "redis", "postgres", "amqp"] as const;
+export const MESSAGE_QUEUE = [
+  "denokv",
+  "redis",
+  "postgres",
+  "mysql",
+  "amqp",
+] as const;
 
 /** All supported key-value store backend identifiers. */
-export const KV_STORE = ["denokv", "redis", "postgres"] as const;
+export const KV_STORE = ["denokv", "redis", "postgres", "mysql"] as const;
 
 /**
  * External database services that need to be running for integration tests.
  * Used by the test suite to check service availability before running tests.
  */
-export const DB_TO_CHECK = ["redis", "postgres", "amqp"] as const;
+export const DB_TO_CHECK = ["redis", "postgres", "mysql", "amqp"] as const;

packages/init/src/json/db-to-check.json

@@ -9,6 +9,11 @@
     "defaultPort": 5432,
     "documentation": "https://www.postgresql.org/download/"
   },
+  "mysql": {
+    "name": "MySQL/MariaDB",
+    "defaultPort": 3306,
+    "documentation": "https://dev.mysql.com/doc/mysql-installation-excerpt/en/"
+  },
   "amqp": {
     "name": "RabbitMQ",
     "defaultPort": 5672,