When we first implemented the datagrids, it was the case that assigning a list value into a TextField would serialize it as a comma-separated list of the values in the list. This is no longer the case, and setting the datagrid columns would end up saving as a list repr, which wasn't parsable when loading the value back out. This change fixes it so we explicitly join the datagrid columns when saving them back to the profile, and adds some unit tests to make sure that saving the columns and sort order work correctly. Testing Done: - Ran unit tests. - Enabled, disabled, and moved some columns around and saw that it got properly saved to the profile.