Transition from Symantec timestamping service to DigiCert timestamping service

[dtivel]

Between October 4th, 2022 and October 24, 2022 we will transition from the deprecated Symantec timestamping service currently in use to the DigiCert timestamping service for both Microsoft author signing and NuGet.org repository signing NuGet packages for new package submissions only.

• October 4th – October 24th: Update NuGet.org repository signing to use http://timestamp.digicert.com. Although all environments (DEV, INT, and PROD) will be updated during this window, http://nuget.org (PROD) specifically will be updated only near the beginning and end of this window.
• October 18th – 20th: Update Microsoft author signing to use http://timestamp.digicert.com.

We expect a smooth and quiet transition; however, if you have questions or concerns, either contact support@nuget.org or post here.

Please see dotnet/core#7688 and Proposal to re-enable signed NuGet package verification for context.

[dtivel]

This was completed early (10/18).