Adding changes to separate unit tests and integration tests (#13670)

* Introducing unit (not integration) tests for the app layer

* Initial support for unit tests at the API

* Adding unit tests support to the store layer

* Add unit tests support in commands

* Adding last tests needed for run unit tests properly

* Fixing govet

* Removing some duplication

* Fixing tests

* Fixing tests

* Not compiling test helpers with the main module for api

* Revert "Not compiling test helpers with the main module for api"

This reverts commit 36a199bbe0f7503f665f5d6c7b41c53aabc2e54f.

* Fixing tests

* Fixing unit tests

* More consistency between api4/apiteslib.go and app/helper_test.go

* Renaming things to make more obvious the new Setup functions purpose

* Reverting change in go.sum

* Start with empty mock for app layer

* Start with empty mock for api layer

* Start with empty mock for web layer

* Renaming SetupWithStoreMockConfig to SetupConfigWithStoreMock

* Fixing tests on web package

* Removing unnecesary function

app/email_batching_test.go

@@ -14,7 +14,7 @@ import (
 )
 
 func TestHandleNewNotifications(t *testing.T) {
-	th := Setup(t)
+	th := SetupWithStoreMock(t)
 	defer th.TearDown()
 
 	id1 := model.NewId()
@@ -265,7 +265,7 @@ func TestCheckPendingNotificationsCantParseInterval(t *testing.T) {
  * Ensures that post contents are not included in notification email when email notification content type is set to generic
  */
 func TestRenderBatchedPostGeneric(t *testing.T) {
-	th := Setup(t)
+	th := SetupWithStoreMock(t)
 	defer th.TearDown()
 
 	var post = &model.Post{}
@@ -290,7 +290,7 @@ func TestRenderBatchedPostGeneric(t *testing.T) {
  * Ensures that post contents included in notification email when email notification content type is set to full
  */
 func TestRenderBatchedPostFull(t *testing.T) {
-	th := Setup(t)
+	th := SetupWithStoreMock(t)
 	defer th.TearDown()
 
 	var post = &model.Post{}