* Use properly `cache()` for the `Mono` in the `ClientRSocketConnector`
* Don't require a `publisherElementTypeExpression` in the
`RSocketOutboundGateway`: the target element type is determined
automatically in the `DefaultRequestSpec.toResponseSpec()`
* SF has deprecated `MediaType.APPLICATION_JSON_UTF8`: fix all its usage
in favor of recommendations to use the `MediaType.APPLICATION_JSON` instead
* Also fix plain `application/json;charset=UTF-8` literals to use
`MediaType.APPLICATION_JSON` instead
* Introduce a `ClientRSocketConnector` to represent a common logic for
client side connection and management an obtained `RSocket`
* Rework the `RSocketOutboundGateway` to perform similar RSocket request
logic on the server side as well.
* Refactor `RSocketOutboundGatewayIntegrationTests` to demonstrate that
RSocket requests work the same way from the server side as well.
For this reason a `CommonConfig` has been extracted with the same
`RSocketOutboundGateway` configuration reuse on both server and client
sides.
* Add initial support for RSockets
* Add `spring-integration-rsocket` module and respective dependencies
* Implement `RSocketOutboundGateway` based on the Spring Messaging
`RSocketRequester`.
This component supports dynamic RSocket properties via expressions
against request message.
to handle `Publisher` for requests, it must be present in the request
message `payload` instead of `FluxMessageChannel` upstream, since the
last one just flattens events to be handled in the `MessageHandler` one
by one.
The result `Mono` is subscribed downstream in the `FluxMessageChannel`
or directly by the `AbstractReplyProducingMessageHandler`.
If result is a `Flux` it is just wrapped into the `Mono` to be processed
downstream by end-user code.
The point is that these request/replies are volatile and live in the
particular context meanwhile a `FluxMessageChannel` is long living
publisher in the application context boundaries.
* The `RSocketOutboundGatewayIntegrationTests` is an adapted copy of
`RSocketClientToServerIntegrationTests` from Spring Messaging
* Add `doOnError()` into the `Flux` created in the
`AbstractMessageProducingHandler` for `Publisher` replies
* * Use singular for the `RSocket` term
* Use no-op `Consumer` for the `strategiesConfigurer` and
`factoryConfigurer` in the `RSocketOutboundGateway` and also
`Assert.notNull()` in the appropriate setters to avoid null check during
`RSocketRequester.builder()` initialization
* Use `TcpServer.create().port(0)` in the
`RSocketOutboundGatewayIntegrationTests` to allow to select free OS port
and bind into it.
The selected port is used later for client configuration in the
`RSocketOutboundGateway` bean definition
* * Change `RSocketOutboundGatewayIntegrationTests.PORT` to lower case
