Joplin-server environment variables for UID and GID

It would sure be nice if joplin-server's Dockerfile accepted environment variables for the UID and GID (and even username) of the running process. I just spent a good amount of time figuring out how to set the file permission correctly for "STORAGE_DRIVER=Type=Filesystem", as well as why ps and top show it running as a completely different user than joplin.