fix(dashboard, fulfilment): fulfilment providers enabled check (#9415)

**What**
- hide disabled fulfilment providers on the admin
- check if the fulfilment provider has an identifier when loading providers

---

FIXES CC-549

packages/modules/fulfillment/src/services/fulfillment-provider.ts

@@ -33,6 +33,12 @@ export default class FulfillmentProviderService extends ModulesSdkUtils.MedusaIn
     providerClass: Constructor<IFulfillmentProvider>,
     optionName?: string
   ) {
+    if (!(providerClass as any).identifier) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_ARGUMENT,
+        `Trying to register a fulfillment provider without an identifier.`
+      )
+    }
     return `${(providerClass as any).identifier}_${optionName}`
   }