Add support for jobs & queueables, migrations

- Create migration directives & migrators
- Modify Cache classes to support array manipulation
- Create Redis unit and RedisCache implementation
- Create Queueable base class and Queue class that uses Cache backend

src/util/cache/Cache.ts

@@ -15,8 +15,9 @@ export abstract class Cache {
      * Store the given value in the cache by key.
      * @param {string} key
      * @param {string} value
+     * @param expires
      */
-    public abstract put(key: string, value: string): Awaitable<void>;
+    public abstract put(key: string, value: string, expires?: Date): Awaitable<void>;
 
     /**
      * Check if the cache has the given key.
@@ -30,4 +31,38 @@ export abstract class Cache {
      * @param {string} key
      */
     public abstract drop(key: string): Awaitable<void>;
+
+    /**
+     * Fetch an item from the cache by key, and then remove it.
+     * @param key
+     */
+    public abstract pop(key: string): Awaitable<string|undefined>;
+
+    /**
+     * Increment a key in the cache by a given amount.
+     * @param key
+     * @param amount
+     */
+    public abstract increment(key: string, amount?: number): Awaitable<number|undefined>;
+
+    /**
+     * Decrement a key in the cache by a given amount.
+     * @param key
+     * @param amount
+     */
+    public abstract decrement(key: string, amount?: number): Awaitable<number|undefined>;
+
+    /**
+     * Push an item onto the end an array-like key.
+     * @param key
+     * @param value
+     */
+    public abstract arrayPush(key: string, value: string): Awaitable<void>;
+
+    /**
+     * Remove and return an item from the beginning of an array-like key.
+     * @param key
+     * @param value
+     */
+    public abstract arrayPop(key: string): Awaitable<string|undefined>;
 }