Hasura and Auth0 - setting up custom claims

Question

Following the Hasura tutorial I've added the following action:

function (user, context, callback) {
  const namespace = "https://hasura.io/jwt/claims";
  context.accessToken[namespace] =
    {
      'x-hasura-default-role': 'user',
      // do some custom logic to decide allowed roles
      'x-hasura-allowed-roles': ['user'],
      'x-hasura-user-id': user.user_id
    };
  callback(null, user, context);
}

I don't follow the comment "do some custom logic to decide allowed roles" - how would I add such custom logic?

I'd like to have to sign up forms, one which would create 'users' in the system and one which will create 'admins', but it's unclear fro the documentation how this is supposed to be achieved.

Do I need to store the user type in the Hasura database then upon logging in using the action above to query the user database and assigning the appropriate rule to the user?

In which case how would I distinguish how someone has signed up to be an admin or a user? The sync users action from the Hasura documentation doesn't explain how I can tell users apart?

function (user, context, callback) {
  const userId = user.user_id;
  const nickname = user.nickname;
  
  const admin_secret = "xxx";
  const url = "yyyyy";
  const query = `mutation($userId: String!, $nickname: String) {
    insert_users(objects: [{
      id: $userId, name: $nickname
    }], on_conflict: {constraint: users_pkey, update_columns: [last_seen, name]}
    ) {
      affected_rows
    }
  }`;
  const variables = { "userId": userId, "nickname": nickname };
  request.post({
      url: url,
      headers: {'content-type' : 'application/json', 'x-hasura-admin-secret': admin_secret},
      body: JSON.stringify({
        query: query,
        variables: variables
      })
  }, function(error, response, body){
       console.log(body);
       callback(null, user, context);
  });
}