The RPC subsystem is where the common framework for handling incoming JSON requests is implemented.

Components

See the common subfolder.

AnyHandler: The type-erased wrapper that allows for storing different handlers in one map/vector.
RpcSpec/FieldSpec: The RPC specification classes, used to specify how incoming JSON is to be validated before it's parsed and passed on to individual handler implementations.
Validators/Modifiers: A bunch of supported validators and modifiers that can be specified as requirements for each FieldSpec to make up the final RpcSpec of any given RPC handler.

Implementing a handler

See tests/unit/rpc for examples.

Handlers need to fulfil the requirements specified by the SomeHandler concept (see rpc/common/Concepts.hpp):

Expose types:
- Input - The POD struct which acts as input for the handler
- Output - The POD struct which acts as output of a valid handler invocation
Have a spec(uint32_t) member function returning a const reference to an RpcSpec describing the JSON input for the specified API version.
Have a process(Input) member function that operates on Input POD and returns HandlerReturnType<Output>
Implement value_from and value_to support using tag_invoke as per boost::json documentation for these functions.