The request for branches on the registration form returns too much information

[yearofthedan]

The api returns a list of branches with which to populate the select field for the signup form. This payload includes additional details such as contact information which is currently only available in the admin view and not required for signup.

We should update the endpoint (or create a new one if it is shared) to return only the information required by the form.

[camjackson]

More info:

• Here is the select box that shows the list of branches for new signups to pick from. Note that it only shows if there's more than one branch present, and it looks like it only need the branch IDs and names.
• Here is the saga that fetches that data
• Here is the relevant API route, which currently returns all information about the branches.
• Here is where the admin dashboard fetches branches. It's actually a different endpoint, which is good.
• Here is that admin endpoint- this shouldn't need changing

I think really all that this issue needs is for the unauthenticated /branches endpoint to limit the info it returns.

[camjackson]

Fixed in #92.