Add ability to toggle attachments and mockups for custom fields Merged

We have several custom fields added to our feature cards and there does not appear to be a way to turn off the capability to attach a file or mockup to the fields which has led to people attaching to various places on the card.

This causes an issue with our Azure and JIRA integrations as attachments are only shared if attached to the "description" field which is really the only place we prefer attachments to be included.