Add .WithClientAssertion to support client assertions

ADAL supports ClientAssertions. We will need to support the same in MSAL. See more:

• ADAL FAQ
• ADAL ClientAssertion Description

Note: This looks very similar to UserAssertion

Describe the solution you’d like We should follow the new model of .With in the API With Claims:

Dictionary<string, string> claims = new[] 
{
 { "client_ip", ipAddres}
};

IClientAssertion clientAssertion = CreateClientAssertion(certificate, claims);
var app = ConfidentialClientApplicationBuilder.Create(clientId)
                      .WithClientAssertion(clientAssertion))
                      .Build();

With Signed assertion:

string SignedAssertion = 
          string.Concat(token, ".", UrlEncodeSegment(credential.Sign(certificate, token)));

IClientAssertion clientAssertion = CreateClientAssertion(SignedAssertion);
var app = ConfidentialClientApplicationBuilder.Create(clientId)
                      .WithClientAssertion(clientAssertion))
                      .Build();

Describe alternatives you’ve considered N/A

Additional context We have a current ask from customers for adding this to be able to move to MSAL.

[jmprieur]

this is now available in MSAL.NET 4.1

[jmprieur]

@henrik-me : something like ^^