REST API example requires API keys

[dylanlt]

Describe the bug
Getting the example integration for REST running is hampered by a requirement for Xero API keys. There should be a REST API example that doesn't require API keys.

To Reproduce
Steps to reproduce the behavior:

1. Follow the example REST API integration documentation; the first step is registration with Xero to obtain API keys

Expected behavior
The REST API example works out the box without additional dependencies.

Actual behavior
The user needs to register with Xero to get API keys.

Additional context
The Xero example is great to demonstrate OAuth, but not as familiar to the developer audience as a Google Cloud, Microsoft Azure, Atlassian Jira, AWS, Okta or Auth0. It's also very niche. I would recommend a simple REST API example and a separate OAuth example using a public cloud provider.

[dylanlt]

Update: While the Xero example requires API keys, the REST example in fact does not require any API keys. Closing.