Chore/rm main entity concept (#7709)

**What**
Update the `MedusaService` class, factory and types to remove the concept of main modules. The idea being that all method will be explicitly named and suffixes to represent the object you are trying to manipulate.
This pr also includes various fixes in different modules

Co-authored-by: Stevche Radevski <4820812+sradevski@users.noreply.github.com>
Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

integration-tests/modules/__tests__/notification/admin/notification.spec.ts

@@ -40,8 +40,8 @@ medusaIntegrationTestRunner({
             resource_type: "order",
           } as CreateNotificationDTO
 
-          const result = await service.create(notification)
-          const fromDB = await service.retrieve(result.id)
+          const result = await service.createNotifications(notification)
+          const fromDB = await service.retrieveNotification(result.id)
 
           expect(result).toEqual(
             expect.objectContaining({
@@ -94,7 +94,9 @@ medusaIntegrationTestRunner({
             channel: "sms",
           } as CreateNotificationDTO
 
-          const error = await service.create(notification).catch((e) => e)
+          const error = await service
+            .createNotifications(notification)
+            .catch((e) => e)
           expect(error.message).toEqual(
             "Could not find a notification provider for channel: sms"
           )
@@ -113,9 +115,11 @@ medusaIntegrationTestRunner({
             template: "product-created",
           } as CreateNotificationDTO
 
-          await service.create([notification1, notification2])
+          await service.createNotifications([notification1, notification2])
 
-          const notifications = await service.list({ channel: "log" })
+          const notifications = await service.listNotifications({
+            channel: "log",
+          })
           expect(notifications).toHaveLength(1)
           expect(notifications[0]).toEqual(
             expect.objectContaining({
@@ -139,9 +143,12 @@ medusaIntegrationTestRunner({
             template: "product-created",
           } as CreateNotificationDTO
 
-          const [first] = await service.create([notification1, notification2])
+          const [first] = await service.createNotifications([
+            notification1,
+            notification2,
+          ])
 
-          const notification = await service.retrieve(first.id)
+          const notification = await service.retrieveNotification(first.id)
           expect(notification).toEqual(
             expect.objectContaining({
               to: "test@medusajs.com",
@@ -176,7 +183,7 @@ medusaIntegrationTestRunner({
           })
           await subscriberExecution
 
-          const notifications = await service.list()
+          const notifications = await service.listNotifications()
 
           expect(logSpy).toHaveBeenLastCalledWith(
             `Attempting to send a notification to: 'test@medusajs.com' on the channel: 'email' with template: 'order-created-template' and data: '{\"order_id\":\"1234\"}'`