The schema still imposes the following restrictions: - Having "template" present makes "content" and "id" required. - Having "content" present makes "template" and "id" required. Template and content are dependent on eachother because we do not know how to interpret content without a template and we a template with no content to interpret is useless. If we have a template and content, then we also need an ID for the message because we cannot reference the message content except by its ID. Differential Revision: https://phabricator.services.mozilla.com/D172458