[Documentation] Message handlers are not documented

[stijnherreman]

Documentation related to component

MicrosoftIdentityUserAuthenticationMessageHandler and MicrosoftIdentityAppAuthenticationMessageHandler

Please check all that apply

• typo
• documentation doesn't exist
• documentation needs clarification
• error(s) in the example
• needs an example

Description of the issue

I discovered the existence of the message handlers by chance in #1131 by browsing the issues. A message handler is the first thing that I went looking for, to use with a typed client generated from an OpenAPI spec.
There are currently no Wiki pages describing these, search engines only come up with the API documentation (when you already know the class names), and there are no examples besides unit tests.

[jmprieur]

thanks @stijnherreman
You shouldn't use these 2 classes, which are legacy and should be obsoleted

Rather use MicrosoftIdentityMessageHandler which is documented. See https://github.com/AzureAD/microsoft-identity-web/blob/master/docs/calling-downstream-apis/custom-apis.md#microsoftidentitymessagehandler---for-httpclient-integration

[bgavrilMS]

Let's treat this as a low-priority bug. Obsoleting old APIs is a usability issue.

[stijnherreman]

Thank you for the clarification, I've got it working with that handler now.