sequenceDiagram
  participant U as User
  participant A as App
  participant P as Provider
  U->>A: Click "Sign in"
  A->>P: Redirect to /authorize
  P-->>U: Login prompt
  U->>P: Credentials
  P-->>A: Code
  A->>P: Exchange for token
  P-->>A: access_token
  A-->>U: Signed in