NAA Auth Changes

[stephenegriffin]

https://devblogs.microsoft.com/microsoft365dev/new-nested-app-authentication-for-office-add-ins-legacy-exchange-tokens-off-by-default-in-october-2024/

[stephenegriffin]

https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/faq-nested-app-auth-outlook-legacy-tokens

[stephenegriffin]

https://learn.microsoft.com/en-us/office/dev/add-ins/develop/enable-nested-app-authentication-in-your-add-in

[stephenegriffin]

No rush because first line to get headers is via API, but fallback of rest will stop working. Others going through this can be found here: https://github.com/OfficeDev/office-js/issues?q=is%3Aissue+naa+is%3Aclosed

[stephenegriffin]

https://github.com/OfficeDev/Office-Add-in-samples/tree/main/Samples/auth/Outlook-Add-in-SSO-NAA-IE

[stephenegriffin]

The more I look at this...the more I think we're fine doing nothing. MHA uses getAllInternetHeadersAsync to get headers for most environments, including every single environment which will be affected by this change. So that should still work. Only if that fails do we fall back to rest and getCallbackTokenAsync, and that should really only happen in downlevel/on prem environments unaffected by this change. Fallback to EWS is third in line and even further downlevel. So I don't think this deprecation is gonna have any noticeable effect on MHA. I'll keep an eye on metrics