Auth tombstones

[BobGerman]

This PR would remove two samples, da-repairs-oauth and da-repairs-oauth-validated, because they are no longer relevant since Teams Toolkit stopped using Easy Auth in declarative agents as of v5.20.

@ericsche - this should remove the need for your PR, #14 which would change the approach to handling the local debug case where Easy Auth is missing. TTK has addressed this in the standard template. Glad to discuss.

Thanks!

[waldekmastykarz]

To me, Easy Auth is a valid way to implement auth, that we should recommend that developers use. For me, it's more secure that doing auth yourself, because it keeps developers on rails. Auth isn't trivial and to do it correctly, you need to have a solid understanding of it. When implementing auth yourself, it's way too easy to miss something crucial and introduce a vulnerability.

Another thing in favor of Easy Auth is, that it's also managed by Microsoft which means that it's kept up to date with the latest findings. I'm aware that not everyone wants or can use Easy Auth, which is why it's good to have options.

Us showing samples isn't related to Teams Toolkit, so even if the tool chooses to show a way to build apps, we can still show alternatives here, in case someone prefers that approach.