Implement session management/authentication to access data post-verification

Part of #18 (closed)

Description

This MR adds logic that submits the credentials to the API to retrieve an access_token which is saved in the store (in memory). This token is then being used by the authenticatedClient which is an axios instance with a request interceptor that adds the Authorization header to the request with the access_token.

Note that the issue does not mention anything about the error flow. The epic only mentions:

• User is notified of success or failure via pop-up alert window (i.e. they are not navigated away from this screen).

So I've not implemented any error display logic other than the alerts.