Possibly breaking down MediaSessionInformation into distinct schema | webrtc-call-handling

[teikuran]

Problem description
The current API definition re-uses the MediaSessionInformation schema, using it as the message body for almost all operations, including POST requests/responses, GET responses, and PUT requests/responses.

This leads to ambiguity e.g., currently, receiverAddress is not marked as required in the MediaSessionInformation schema. This allows a client to technically submit a call initiation request without a destination, which is functionally invalid.

Possible evolution
Separate the schema definition to ensure that each operation has a clear logic implementation e.g., CreateMediaSessionRequest, UpdateSessionStatusRequest for PUT, and etc. Detail proposal is FFS.