Adds CnameApiKey to CustomDomainVerificationResponse (#757)

[tmschlot]

Changes

Please describe both what is changing and why this is important.

• Added CnameApiKey property to CustomDomainVerificationResponse class to support self-managed certificates

References

• CustomDomainVerificationResponse is missing a property for the cname_api_key #757
• POST /custom-domains/:id/verify

Testing

Custom domain tests are limited, as described by the existing tests, which must be run manually. Since no other tests exist to test rudimentary serialization, no tests were added.

• This change adds unit test coverage

• This change adds integration test coverage

• This change has been tested on the latest version of the platform/language or why not

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

[kailash-b]

Hi @tmschlot
Thanks for the contribution.
While the changes look good, we can only merge signed commits.

Can you please sign your commit?
You could follow the instructions here

Apologies for this last minute ask, this has been a recent change and we are updating our ReadMe (contribution guidelines) to include this pre-requisite.

[tmschlot]

@kailash-b... I tried and finally was able to get some correctly signed commits pushed, but I'm afraid I may have screwed up the graph in the process. Let me know if you'd prefer me to close this PR and create a new one with a cleaner graph or if you've got the knowledge/ability to clean this up before merging.

[kailash-b]

@tmschlot - It'd be great if you can close this PR and raise a separate one on the latest - I think it'd be easier than cleaning up this commit graph.

[tmschlot]

Created #764