PLT-7206: Remove the "Delete Channel" option for private channels if you're the last channel member and policy setting restricts channel deletion (#7050)

* PLT-7206: UI changes. Removed last user in channel loophole, refactored code to clean it up, added differentiated support for public and private channels, added unit tests. Still need to implement server-side checks

* PLT-7206: All helper methods in channel_utils.jsx now accept the same three boolean variables in the same order and use the same boolean logic to check their values.

* PLT-7206: Added unit tests for showManagementOptions(...)

* PLT-7206: Fixed test case descriptions

* Added unit tests for showCreateOption(...)

* PLT-7206: Added unit tests for canManageMembers(...)

* PLT-7206: Removed last person in channel loophole from server-side code

* PLT-7206: Reverted config.json

* PLT-7206: Fixed double negatives in unit test names

* PLT-7206: PR feedback - Removed confusing comment and unused variable

api/channel_test.go

@@ -1476,9 +1476,8 @@ func TestDeleteChannel(t *testing.T) {
 		t.Fatal("should have errored not system admin")
 	}
 
-	// Only one left in channel, should be able to delete
-	if _, err := Client.DeleteChannel(channel4.Id); err != nil {
-		t.Fatal(err)
+	if _, err := Client.DeleteChannel(channel4.Id); err == nil {
+		t.Fatal("Should not be able to delete channel, even though only one user is left")
 	}
 
 	th.LoginSystemAdmin()