Distinguish between the "mySharesListURL" and "mySharesRootURL".

For example:

  mySharesListURL: https://spideroak.com/storage/SOMEB32ID/shares
       - where to find the list of share rooms for the account
  mySharesRootURL: https://spideroak.com/share/SOMEB32ID/
       - the base url for share rooms listed on mySharesListURL

Also, replace the accountModel.getStorageURL() and
accountModel.getMyShareRoomsURL() with accountModel.get() calls, in the API
and in various calls.
When adding, prefix the "my share room" models with the right base url -
mySharesRootURL.  This is misguided, however, since the share room fetches
will be resolved against their collection.  (Since the base URLs for the
share rooms list and the contained share rooms, themselves, are composed
differently, then maybe they need to be in different collections?)

Remove the share_id_b32 from the share room url - that part will come from
the collection.

Also, replace accountModel.getMyShareRoomsURL() with an accountModel.get()
call.