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/InMemCache.ts

@@ -1,5 +1,7 @@
 import { Cache } from './Cache'
 import { Collection } from '../collection/Collection'
+import {Awaitable, Maybe} from '../support/types'
+import {ErrorWithContext} from '../error/ErrorWithContext'
 
 /**
  * Base interface for an item stored in a memory cache.
@@ -44,4 +46,61 @@ export class InMemCache extends Cache {
     public async drop(key: string): Promise<void> {
         this.items = this.items.whereNot('key', '=', key)
     }
+
+    public pop(key: string): Awaitable<Maybe<string>> {
+        const existing = this.items.firstWhere('key', '=', key)
+        this.items = this.items.where('key', '!=', key)
+        return existing?.item
+    }
+
+    public async increment(key: string, amount?: number): Promise<number> {
+        const next = parseInt((await this.fetch(key)) ?? '0', 10) + (amount ?? 1)
+        await this.put(key, String(next))
+        return next
+    }
+
+    public async decrement(key: string, amount?: number): Promise<number> {
+        const next = parseInt((await this.fetch(key)) ?? '0', 10) - (amount ?? 1)
+        await this.put(key, String(next))
+        return next
+    }
+
+    public arrayPush(key: string, value: string): Awaitable<void> {
+        const existing = this.items.where('key', '=', key).first()
+        const arr = JSON.parse(existing?.item ?? '[]')
+
+        if ( !Array.isArray(arr) ) {
+            throw new ErrorWithContext('Unable to arrayPush: key is not an array', {
+                key,
+                value,
+            })
+        }
+
+        arr.push(value)
+        if ( existing ) {
+            existing.item = JSON.stringify(arr)
+        } else {
+            this.items.push({
+                key,
+                item: JSON.stringify(arr),
+            })
+        }
+    }
+
+    public arrayPop(key: string): Awaitable<Maybe<string>> {
+        const existing = this.items.where('key', '=', key).first()
+        const arr = JSON.parse(existing?.item ?? '[]')
+
+        const value = arr.pop()
+        if ( existing ) {
+            existing.item = JSON.stringify(arr)
+        } else {
+            this.items.push({
+                key,
+                item: JSON.stringify(arr),
+            })
+        }
+
+        return value
+    }
 }