Token Invalidation

[liampmoore]

If you are logged in too long your token will become invalid, though the token stays in localstorage and the frontend app thinks you are logged in. After that all requests that require authentication (such as requests for your list of favorite cities) will fail.

You can reproduce this issue by staying logged in for more than a day.

We could have the app either log you out if your token is invalid, or implement some sort of token refreshing so that the application periodically sends a request to get a new token from the web backend.