refactor(medusa): Cleanup and fix CartService (#1306)

* refactor(medusa): Cleanup + fix

* styles(medusa): Lint

* refactor(medusa): Finalize cleanup

* feat(medusa): Prefer the usage of bulk operations instead of sequential/conccurent operations

* feat(medusa): Improve cart service

* refactor(medusa): Explicitly specifying protected methods when needed as well as enfore the usage of the local transactionManager_ in those methods

* tests(medusa): Fix tests according to the new changes

* feat(medusa): Cleanup after rebase

* test(medusa): Fix cart service tests

packages/medusa-interfaces/src/base-service.js

@@ -228,8 +228,7 @@ class BaseService {
       }
 
       try {
-        const result = await this.manager_.transaction((m) => doWork(m))
-        return result
+        return await this.manager_.transaction((m) => doWork(m))
       } catch (error) {
         if (errorHandler) {
           const result = await errorHandler(error)