PLT-7537: Move channel CLI command posts system message to channel. (#8161)

* [PTL-7537] implement feature and test

* [PTL-7537] Update feature to post the the room requiring a username flag to be used

* [PTL-7537] update tests with username

* update test to remove changes to the test helper struct

* use the basic team and user

app/channel_test.go

@@ -97,7 +97,7 @@ func TestMoveChannel(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if err := th.App.MoveChannel(targetTeam, channel1); err == nil {
+	if err := th.App.MoveChannel(targetTeam, channel1, th.BasicUser); err == nil {
 		t.Fatal("Should have failed due to mismatched members.")
 	}
 
@@ -105,7 +105,7 @@ func TestMoveChannel(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if err := th.App.MoveChannel(targetTeam, channel1); err != nil {
+	if err := th.App.MoveChannel(targetTeam, channel1, th.BasicUser); err != nil {
 		t.Fatal(err)
 	}
 }