OptionalContextOptionalIncludeOptionalPreviewOptionalProviderThe provider of the request the communication serves; every metadata lookup and read uses it. The API sets it from the request. An in-process caller that leaves it unset gets the process's default provider.
The user the communication runs as. Required on the server: every recipient and related-entity read runs as this user, so row-level security, entity permissions and field-level security all apply, and no field this user cannot read is merged into a message or returned. The server engine refuses a request without it. Clients leave it unset; the API sets it from the authenticated caller.