Bugfixes: Clinic Creation/Joining

[AEst2002]

Resources
For original deliverable(s), see #6 and #15.

Description
There are a few minor issues related to clinic joining and leaving in the current version of the app. Your task is to fix the following issues, and to do your own testing for anything not caught here!

• Clinic Creation
  • If a user already owns a clinic, their clinic name should be autofilled in the input box on the create-clinic screen, and their code should also be readily available on the same screen without the user needing to resubmit the form.
• Clinic Joining/Leaving
  • An error gets displayed when trying to join a clinic the first time, and a user is only able to join the second time they click the join button.
  • Error messages should communicate understandable information to end-users instead of exposing database errors. (e.g., "Something went wrong on our end, please try again later" instead of "Invalid syntax for type uuid: ...")
  • Users should not be able to join the same clinic several time
  • Clinic leaving is still left to be implemented