http proxy for RPC callers

[zerlok]

• allow http clients to use brokrpc callers without knowing about broker
• http proxy will transform http request to RPC caller request and RPC caller response to http final response

example of http proxy handler

async def handle_my_rpc_call(request: MyRequestModel, caller: Caller[MyRequest, MyResponse] = Depends(get_my_rpc_caller)) -> MyResponseModel:
    response = await caller.invoke(_build_caller_request(request))
    return _build_my_response(response)