docs: def begin_auth():
      """ Request authentication token to sign """
  
      repository    = request.headers['repository']
      if repository not in config['repositories']: return fail(no_such_repo_msg)
  
      # ==
      repository_path = config['repositories'][repository]['path']
      conn = auth_db_connect(cpjoin(repository_path, 'auth_transient.db')); gc_tokens(conn)
  
      # Issue a new token
      auth_token = base64.b64encode(pysodium.randombytes(35)).decode('utf-8')
      conn.execute("insert into tokens (expires, token, ip) values (?,?,?)",
                   (time.time() + 30, auth_token, request.environ['REMOTE_ADDR']))
      conn.commit()
  
      return success({'auth_token' : auth_token})