Confirm that site is indeed not a WordPress site after XML-RPC validation fails

More context: https://github.com/wordpress-mobile/WordPress-iOS/issues/18497#issuecomment-1779361108 Related PR https://github.com/wordpress-mobile/WordPress-iOS/pull/21904

In rare cases, XML-RPC validation can fail and indicate that the site is not a WordPress site when it actually is.

To avoid this corner case, I added an additional isWPSite check after guessXMLRPCURL and before showing errors to the users:

If WordPressOrgXMLRPCValidator determines that it's not a valid WordPress site and isWPSite (connect/site-info) API call confirms it, then we inform the user that the site is invalid
If WordPressOrgXMLRPCValidator determines that it's not a valid WordPress site but isWPSite (connect/site-info) API suggests otherwise, we inform users about XML-RPC issues which they can then look for further assistance

Implementation details

I didn't want to change this fragile code before writing tests to it and to write tests I needed to split business logic from UI. I recommend reviewing commit by commit:

Extract error handling code - https://github.com/wordpress-mobile/WordPressAuthenticator-iOS/pull/796/commits/9c14098b737397095420c4bd68cc39ebe1ce8778
Move it to ViewModel - https://github.com/wordpress-mobile/WordPressAuthenticator-iOS/pull/796/commits/b62db739cd3f6d6b20e50947ccc6821c8309e32b
Add unit tests - https://github.com/wordpress-mobile/WordPressAuthenticator-iOS/pull/796/commits/76925ba83e7a6712b7412fc7d849bbb6de457ab8
Add isWPSite check - https://github.com/wordpress-mobile/WordPressAuthenticator-iOS/pull/796/commits/a27ac06167677a7303a4d84d633c0daa6b82fb45

[x] I have considered if this change warrants release notes and have added them to the appropriate section in the CHANGELOG.md if necessary.

wordpress-mobile / WordPressAuthenticator-iOS

Confirm that site is indeed not a WordPress site after XML-RPC validation fails #796

Implementation details