[mgt-chat] Chat components should work with the ProxyProvider to support a confidential client flow

[sebastienlevert]

Proposal: Chat components should work with the ProxyProvider to support a confidential client flow

Description

As part of the work on mgt-chat, it appears that a confidential client flow will be required. The chat components need a story with using the ProxyProvider that would then support a confidential client flow. This is not a required flow for non-premium APIs but brings a broken experience after the initial limits.

Rationale

The billing platform of Microsoft Graph only supports confidential clients.

Preferred Solution

Provide a working and deployable ProxyProvider solution and samples.