Add support for App Callback URLs

[Roming22]

Fixes: #3203

[gmlewis]

This change makes no sense to me, based on line 117 above it.
Note that both fields have identical JSON bindings, which means they get mapped to the same thing:

	URL *string `json:"url,omitempty"`
CallbackURL *string `json:"url,omitempty"`

[Roming22]

You're absolutely right. I should have copied the code from my test, but didn't.
It's now fixed.

[gmlewis]

Thank you, @Roming22 !
Could I please trouble you to add the GitHub API Docs URL as a comment to this code that shows where this is documented?
I know this is the scrape directory, but it would be nice to have a reference to it.
Thanks again!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.92%. Comparing base (2b8c7fa) to head (d7769ed).
Report is 79 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3204 +/- ##
==========================================
- Coverage 97.72% 92.92% -4.80% 
==========================================
Files 153 171 +18 Lines 13390 11582 -1808 ==========================================
- Hits 13085 10763 -2322 - Misses 215 726 +511 - Partials 90 93 +3 

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[Roming22]

Thank you, @Roming22 ! Could I please trouble you to add the GitHub API Docs URL as a comment to this code that shows where this is documented? I know this is the scrape directory, but it would be nice to have a reference to it. Thanks again!

I do not know where, or whether, it is documented. I look at the surrounding fields and made a lucky guess.

[Roming22]

Found it!
Link added as a comment. Please check that it looks like the right one to you too.

[gmlewis]

Thank you, @Roming22 !
LGTM.
Merging.

[Roming22]

Thanks for the support @gmlewis!

Is there an ETA for the next release?

[gmlewis]

It looks like it is about time. I'll work on it.

[gmlewis]

This is now available here: https://github.com/google/go-github/releases/tag/v63.0.0