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/service/Queueables.ts

@@ -0,0 +1,25 @@
+import {CanonicalStatic} from './CanonicalStatic'
+import {Singleton, Instantiable, StaticClass} from '../di'
+import {CanonicalDefinition} from './Canonical'
+import {Queueable} from '../support/queue/Queue'
+
+/**
+ * A canonical unit that resolves Queueable classes from `app/queueables`.
+ */
+@Singleton()
+export class Queueables extends CanonicalStatic<Queueable, Instantiable<Queueable>> {
+    protected appPath = ['queueables']
+
+    protected canonicalItem = 'job'
+
+    protected suffix = '.job.js'
+
+    public async initCanonicalItem(definition: CanonicalDefinition): Promise<StaticClass<Queueable, Instantiable<Queueable>>> {
+        const item = await super.initCanonicalItem(definition)
+        if ( !(item.prototype instanceof Queueable) ) {
+            throw new TypeError(`Invalid middleware definition: ${definition.originalName}. Controllers must extend from @extollo/lib.Queueable.`)
+        }
+
+        return item
+    }
+}