MM-34002: Improve AddUserToChannel (#17174)

* MM-34002: Improve AddUserToChannel

When we would add a user to a channel, we would
check whether the user is removed from that team or not.

During LDAP sync, this check is not required because the
team member would have just been created. Hence, we
pass a boolean flag to bypass the check.

And with that done, we can freely query the replica.

https://mattermost.atlassian.net/browse/MM-34002

```release-note
NONE
```

* Refactor code

* Rename a struct field

* fix double negative

services/sharedchannel/mock_AppIface_test.go

@@ -16,13 +16,13 @@ type MockAppIface struct {
 	mock.Mock
 }
 
-// AddUserToChannel provides a mock function with given fields: user, channel
-func (_m *MockAppIface) AddUserToChannel(user *model.User, channel *model.Channel) (*model.ChannelMember, *model.AppError) {
-	ret := _m.Called(user, channel)
+// AddUserToChannel provides a mock function with given fields: user, channel, skipTeamMemberIntegrityCheck
+func (_m *MockAppIface) AddUserToChannel(user *model.User, channel *model.Channel, skipTeamMemberIntegrityCheck bool) (*model.ChannelMember, *model.AppError) {
+	ret := _m.Called(user, channel, skipTeamMemberIntegrityCheck)
 
 	var r0 *model.ChannelMember
-	if rf, ok := ret.Get(0).(func(*model.User, *model.Channel) *model.ChannelMember); ok {
-		r0 = rf(user, channel)
+	if rf, ok := ret.Get(0).(func(*model.User, *model.Channel, bool) *model.ChannelMember); ok {
+		r0 = rf(user, channel, skipTeamMemberIntegrityCheck)
 	} else {
 		if ret.Get(0) != nil {
 			r0 = ret.Get(0).(*model.ChannelMember)
@@ -30,8 +30,8 @@ func (_m *MockAppIface) AddUserToChannel(user *model.User, channel *model.Channe
 	}
 
 	var r1 *model.AppError
-	if rf, ok := ret.Get(1).(func(*model.User, *model.Channel) *model.AppError); ok {
-		r1 = rf(user, channel)
+	if rf, ok := ret.Get(1).(func(*model.User, *model.Channel, bool) *model.AppError); ok {
+		r1 = rf(user, channel, skipTeamMemberIntegrityCheck)
 	} else {
 		if ret.Get(1) != nil {
 			r1 = ret.Get(1).(*model.AppError)

services/sharedchannel/service.go

@@ -42,7 +42,7 @@ type AppIface interface {
 	SendEphemeralPost(userId string, post *model.Post) *model.Post
 	CreateChannelWithUser(channel *model.Channel, userId string) (*model.Channel, *model.AppError)
 	GetOrCreateDirectChannel(userId, otherUserId string, channelOptions ...model.ChannelOption) (*model.Channel, *model.AppError)
-	AddUserToChannel(user *model.User, channel *model.Channel) (*model.ChannelMember, *model.AppError)
+	AddUserToChannel(user *model.User, channel *model.Channel, skipTeamMemberIntegrityCheck bool) (*model.ChannelMember, *model.AppError)
 	AddUserToTeamByTeamId(teamId string, user *model.User) *model.AppError
 	PermanentDeleteChannel(channel *model.Channel) *model.AppError
 	CreatePost(post *model.Post, channel *model.Channel, triggerWebhooks bool, setOnline bool) (savedPost *model.Post, err *model.AppError)

services/sharedchannel/sync_recv.go

@@ -222,7 +222,7 @@ func (scs *Service) upsertSyncUser(user *model.User, channel *model.Channel, rc
 	}
 
 	// add user to channel
-	if _, err := scs.app.AddUserToChannel(userSaved, channel); err != nil {
+	if _, err := scs.app.AddUserToChannel(userSaved, channel, false); err != nil {
 		return nil, fmt.Errorf("error adding sync user to ChannelMembers: %w", err)
 	}
 	return userSaved, nil