Team/Channel members bulk save/update/delete (#14053)

* Members Save Multiple

* Multiple Channel Members implemented

* Working version with member multi save and multi update

* Adding tests to the save multiple team members store methods

* Tests passing for SaveMember

* Adding remove members tests

* Working on channel store tests

* More work on testing properly SaveMember and SaveMultipleMembers on channels

* More work on testing properly SaveMember and SaveMultipleMembers on teams

* Adding tests for update multiple members for team

* Adding tests for update multiple members for channel

* Fixing some tets

* Fixing tests

* Fixing tests

* Fixing i18n

* Addressing govet problems

* Addressing govet problems

* Addressing govet problems

* Addressing govet problems

* Addressing PR comments (and removing TODO)

* Addressing PR comments

* Fixed broken test

* Removing unnecesary i18n translation string

app/helper_test.go

@@ -454,6 +454,11 @@ func (me *TestHelper) AddUserToChannel(user *model.User, channel *model.Channel)
 	return member
 }
 
+func (me *TestHelper) CreateRole(roleName string) *model.Role {
+	role, _ := me.App.CreateRole(&model.Role{Name: roleName, DisplayName: roleName, Description: roleName, Permissions: []string{}})
+	return role
+}
+
 func (me *TestHelper) CreateScheme() (*model.Scheme, []*model.Role) {
 	utils.DisableDebugLogForTest()