[Feature Request] Expose WithClientCapabilities in TokenAcquisitionOptions to declare the client supports CAE / AuthenticationContext

[jmprieur]

Is your feature request related to a problem? Please describe.
Clients (web apps or web APIs calling web APIs) need to support CAE and AuthenticationContext

Describe the solution you'd like
For this we'd want to expose ClientCapabilities in TokenAcquisitionOptions

See also
https://docs.microsoft.com/azure/active-directory/develop/app-resilience-continuous-access-evaluation

[jmprieur]

This is actually possible because ApplicationOptions expose the ClientCapabilities property
https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/7f9974cc0525d308e091dbf380ef6d8c75aad8d9/src/client/Microsoft.Identity.Client/AppConfig/ApplicationOptions.cs#L123

so the way to use client capabilities would be, in the appsettings.json to set

"AzureAD" : 
{
 // usual members
 "ClientCapabilities" : [  "cp1" ]
}

[jmprieur]

cc: @kalyankrishna1 as you were asking about this

[jmprieur]

Added some documentation. See Client capabilities

[jennyf19]

Included in 1.9.0 release