dco-guidelines.md: disallow/allow using @users.noreply.github.com email addresses

[AkihiroSuda]

https://github.com/cncf/foundation/blob/e0060f51/dco-guidelines.md

The key concern is that your identification is sufficient enough to contact you if an issue were to arise in the future about your contribution.

For this concern, the DCO guidelines should explicitly disallow using @users.noreply.github.com email addresses?

[dims]

@AkihiroSuda i have a feeling that as someone's github profile is still unique and folks can be reached by @ addressing them on issues and PRs to get their attention. So i think that passes the test.

Note that the submitter can use any handle they want as long as it is "known" to the folks running the project.

[AkihiroSuda]

i have a feeling that as someone's github profile is still unique and folks can be reached by @ addressing them on issues and PRs to get their attention.

Usually yes, but the person may remove the GitHub account, lose access to the account, or get banned in a bad situation.

(Same applies for the email account too, though)

[dims]

@AkihiroSuda for sure... also can you please read through the background discussion #383 (comment) to get a sense of why the policy is set this way. thanks!

[AkihiroSuda]

Thanks