Signing: Enable ClientPolicies to require use of a set of Trusted Authors and Repos listed in NuGet.Config

[PatoBeltran]

This issue is to track implementation of the feature designed in https://github.com/NuGet/Home/wiki/%5BSpec%5D-NuGet-Config-schema-changes-to-enable-trusted-signers

This is a first step feature to add support for client policies. This issue is tracking the following work:

• Read and parse correctly trusted signers from nuget.config
• Pass down settings from nuget.config to verification API through extraction and verify command.
• Use nuget.config settings in the verification pipeline as an input and use it to verify the package.
• Refactor AllowListVerificationProvider to receive only one allowList.
• Add support for allowUntrustedRoot by using that flag in verify API
• Forbid large package downloads when on require client policy.
• Improve error messages - Signing: improve signing related error messages #6906

[jainaashish]

Can you link this issue to the right spec?

[PatoBeltran]

Closing this issue since the work is done and merged into 15.9 and the missing work for the CLI gesture is being tracked by #7480