fix: make RDP drive redirection writable on the stock deployment (#1333)

* fix: make RDP drive redirection writable on the stock deployment

The default drive-path was /drive on the guacd side, which the official
guacd image cannot create as its non-root user, so every upload was
refused with guacd's raw "FAIL (CANNOT OPEN)" ack. Default to
GUACD_DRIVE_PATH (set to the shared termix-data volume in compose) with
one folder per user, and explain guacd's refusal in the file browser.

* style: format RDP drive settings

docker/compose-dev.yml

@@ -15,6 +15,7 @@ services:
       GUACD_HOST: "guacd-dev"
       GUACD_TUNNEL_HOST: "termix-dev"
       GUACD_RECORDING_PATH: "/termix-data/session_recordings/guacamole"
+      GUACD_DRIVE_PATH: "/termix-data/rdp-drive"
     depends_on:
       - guacd-dev
     networks:

docker/docker-compose.yml

@@ -12,6 +12,9 @@ services:
       GUACD_HOST: "guacd"
       GUACD_TUNNEL_HOST: "termix"
       GUACD_RECORDING_PATH: "/termix-data/session_recordings/guacamole"
+      # Where guacd stores files for RDP drive redirection (one folder per
+      # user is created underneath). Must be writable by guacd's user.
+      GUACD_DRIVE_PATH: "/termix-data/rdp-drive"
       # Hardened deployments can require keys from environment variables or
       # Docker secrets mounted through JWT_SECRET_FILE, DATABASE_KEY_FILE,
       # ENCRYPTION_KEY_FILE and INTERNAL_AUTH_TOKEN_FILE.