Test: improve tests by checking error messages (#549)

Resolve #544.

Ensure cache is used for tokens

Merge pull request #352 from bartdesmet/dev/bartde/enable_msal_logging

Merge pull request #351 from dotnet/hold-auth-context

Ensure auth context is reused across calls for caching

Update to reflect main branch name

Merge pull request #202 from AArnott/fix197

Return exit code 3 from SignClient when no files will be signed

Merge pull request #133 from dotnet/client-fixes

Client fixes

Merge pull request #125 from dotnet/client-globbing

Add globbing support and concurrency.

Use FileMode.Create to ensure we do't leave parts of an existing file…

… in case of overwrite

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