Save a project as a template

Copy the project (document and files) into a user template of its workspace. Saving again from the same project overwrites that template and keeps its id; deleting the project does not affect it. Start it with POST /projects and template_id. fields replaces the project's template fields first, each named by its path: clips.<clip_id>.<property> (e.g. clips.<id>.text, clips.<id>.style.color), display.<property>, or media.<media_id>.url for the file behind a media. Omitted, the fields set in the editor are kept.