Add option to include response headers in the result

[adamjmcgrath]

Changes

Adding an option includeResponseHeaders to the Management Client so that you can get the response headers as well as the payload in the result of each method. eg

const mgmt = new ManagementClient();
const mgmt2 = new ManagementClient({ includeResponseHeaders: true });

const users = await mgmt.getUsers();
const { data: users, headers } = await mgmt2.getUsers();

mgmt.getUsers((err, users) => {
  console.log(users);
});
mgmt.getUsers((err, { data: users, headers }) => {
  console.log(users);
});

This is useful for users that want to use a different rate limit retry strategy than the exponential backoff on 429 used by this SDK (Like the one described here https://auth0.com/docs/troubleshoot/customer-support/operational-policies/rate-limit-policy#handle-rates-limitations-in-code)

References

fixes #742 #741

Testing

Please describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. If this library has unit and/or integration testing, tests should be added for new functionality and existing tests should complete without errors.

• This change adds unit test coverage

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors

[adamjmcgrath]

Here we are always using the restClient (rest-facade)'s callback method because this is the only one that returns both the body of the response and the headers

[Widcket]

LGTM. Just added a missing period to the API docs.