Add arg for configuring unix socket perms (#1103)

The default unix socket permissions of 600 is too restrictive for many use
cases.

Added a new argument --unix-socket-perms which is passed to waitress to allow
for user configurable socket permissions

app/routes.py

@@ -626,6 +626,11 @@ def run_app() -> None:
         default='',
         metavar='</path/to/unix.sock>',
         help='Listen for app on unix socket instead of host:port')
+    parser.add_argument(
+        '--unix-socket-perms',
+        default='600',
+        metavar='<octal permissions>',
+        help='Octal permissions to use for the Unix domain socket (default 600)')
     parser.add_argument(
         '--debug',
         default=False,
@@ -677,7 +682,7 @@ def run_app() -> None:
     if args.debug:
         app.run(host=args.host, port=args.port, debug=args.debug)
     elif args.unix_socket:
-        waitress.serve(app, unix_socket=args.unix_socket)
+        waitress.serve(app, unix_socket=args.unix_socket, unix_socket_perms=args.unix_socket_perms)
     else:
         waitress.serve(
             app,