Make it possible to stream "application/grpc" in Spring MVC via Flux<T> #35401
Description
It is possible with ResponseBodyEmitter, but for Flux, given that message converters are used for individual items, it is necessary to know the streaming format in order to also insert any required delimiters. This why only specific media types are supported such as SSE, newline-delimited JSON, and plain text.
In contrast, the same is possible in WebFlux where an HttpMessageWriter handles the whole Flux and can make decisions for the full output.
In gRPC streaming, each Protobuf message includes a content-length, so there is no need for delimiters. It should be easy to plug it into our existing Flux support.