fix(extension): extend JWT auth token expiration for extension EE-3065 (#6881)

The default expiration time of 8 hours does not make sense in the
context of the docker desktop extension. This adds a new feature flag
which can be enabled with `export DOCKER_EXTENSION=1` and when 
present will set the expiration time to 99 years.

I've set this flag in the docker-compose.yml we use when building our
docker extension.

build/docker-extension/docker-compose.yml

@@ -5,6 +5,8 @@ services:
     image: ${DESKTOP_PLUGIN_IMAGE}
     command: ['--admin-password', '$$$$2y$$$$05$$$$bsb.XmF.r2DU6/9oVUaDxu3.Lxhmg1R8M0NMLK6JJKUiqUcaNjvdu']
     restart: unless-stopped
+    environment:
+      - DOCKER_EXTENSION=1
     security_opt:
       - no-new-privileges:true
     volumes: