The purpose of this milestone is to fully establish the user's session and coaching session so that all of the rest of the coaching session page information can be loaded for the coach and the coachee.

Definition of done:

1. Both a coach and a coachee user can log in at the same time.
2. When a coach or coachee navigates to their coaching session page, the URL includes their coaching_sessions.external_id properly. Proper selection is done through the following algorithm:
   a. The last selected coaching_session.id gets stored in a client side cookie that is automatically used the next time a user logs in
   b. If this client side cookie doesn’t exist, automatically select the next closest scheduled session is automatically selected and the cookie is created
   c. If there isn’t a next closest scheduled session, select the last conducted session from the past
3. For both types of users, their default organization and coaching relationship can automatically be "selected" by the backend and communicated to the frontend. By default, this should be the first organization that the user was associated with and the first coaching relationship linked to another user (i.e. to a coach or coachee).
4. The backend will offer an API endpoint to set the default organization for a given user.
5. The backend will offer an API endpoint to set the default coaching relationship for a given user.