ChannelStore migration Part 2 (#15405)

* Migration completed

* Several corrections in tests

* Fix imports

* Fix some errors after testing

* Trigger CI

* Fix tests

* Suggestions

* Suggestions

* Add license

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/syncables_test.go

@@ -142,7 +142,7 @@ func TestCreateDefaultMemberships(t *testing.T) {
 	}
 
 	_, err = th.App.GetChannelMember(experimentsChannel.Id, scientist1.Id)
-	if err.Id != "store.sql_channel.get_member.missing.app_error" {
+	if err.Id != "app.channel.get_member.missing.app_error" {
 		t.Errorf("wrong error: %s", err.Id)
 	}
 
@@ -184,7 +184,7 @@ func TestCreateDefaultMemberships(t *testing.T) {
 	}
 
 	_, err = th.App.GetChannelMember(experimentsChannel.Id, scientist1.Id)
-	if err.Id != "store.sql_channel.get_member.missing.app_error" {
+	if err.Id != "app.channel.get_member.missing.app_error" {
 		t.Errorf("wrong error: %s", err.Id)
 	}