Feat(fulfillment): service provider registration + fulfillment management (#6524)

**What**
- Create the fulfillment manual package with a first iteration API 
- Create a new `AbstractFulfillmentProviderService` and `IFulfillmentProvider`
- Modify the module service interface to add new methods to manipulate the fulfillment and the communication with the external provider
  - create (no bulk)
  - cancel (no bulk)
  - update (no bulk)
  - list
  - listAndCount
  - retrieve
- Add new methods to the service provider service to include communication with the third party provider
  - get options
  - create
  - cancel
  - validate data
  - validate option
- Update/create interfaces and DTO's
- fix repository serializer to allow non entity to be passed without throwing
- split module tests into multiple files to simplify navigation
- Add integration tests to validate fulfillments manipulation and external provider loading + communication

FIXES CORE-1729
FIXES CORE-1785
FIXES CORE-1784
FIXES CORE-1766

packages/fulfillment-manual/src/services/manual-fulfillment.ts

@@ -0,0 +1,44 @@
+import { AbstractFulfillmentProviderService } from "@medusajs/utils"
+
+// TODO rework type and DTO's
+
+export class ManualFulfillmentService extends AbstractFulfillmentProviderService {
+  static identifier = "manual"
+
+  constructor() {
+    super()
+  }
+
+  async getFulfillmentOptions(): Promise<Record<string, unknown>[]> {
+    return [
+      {
+        id: "manual-fulfillment",
+      },
+      {
+        id: "manual-fulfillment-return",
+        is_return: true,
+      },
+    ]
+  }
+
+  async validateFulfillmentData(
+    optionData: Record<string, unknown>,
+    data: Record<string, unknown>,
+    context: Record<string, unknown>
+  ): Promise<any> {
+    return data
+  }
+
+  async validateOption(data: Record<string, unknown>): Promise<boolean> {
+    return true
+  }
+
+  async createFulfillment(): Promise<Record<string, unknown>> {
+    // No data is being sent anywhere
+    return {}
+  }
+
+  async cancelFulfillment(fulfillment: Record<string, unknown>): Promise<any> {
+    return {}
+  }
+}