Document generated GRPC.Stub function arguments

Adds clarifying documentation for how functions are generated for GRPC.Stub

Closes elixir-grpc#339

lib/grpc/stub.ex

@@ -35,7 +35,12 @@ defmodule GRPC.Stub do
   then use `recv/1` to receive the reply. And if the reply is streaming, `recv/1`
   returns a `Stream`.
 
-  You can refer to `call/6` for doc of your RPC functions.
+  ## RPC Functions
+
+  RPC functions generated via the GRPC.Service.rpc/3 macro are exposed in `GRPC.Stub`
+  module exposing that service.  The following function types are generated:
+
+  ### Unary
   """
   alias GRPC.Channel
   @insecure_scheme "http"
@@ -219,23 +224,6 @@ defmodule GRPC.Stub do
   end
 
   @doc false
-  #  #  The actual function invoked when invoking an RPC function.
-  #
-  #  Returns
-  #
-  #    * Unary calls. `{:ok, reply} | {:ok, headers_map} | {:error, error}`
-  #    * Client streaming. A `GRPC.Client.Stream`
-  #    * Server streaming. `{:ok, Enumerable.t} | {:ok, Enumerable.t, trailers_map} | {:error, error}`
-  #
-  #  Options
-  #
-  #    * `:timeout` - request timeout. Default is 10s for unary calls and `:infinity` for
-  #      client or server streaming calls
-  #    * `:deadline` - when the request is timeout, will override timeout
-  #    * `:metadata` - a map, your custom metadata
-  #    * `:return_headers` - default is false. When it's true, a three elem tuple will be returned
-  #      with the last elem being a map of headers `%{headers: headers, trailers: trailers}`(unary) or
-  #      `%{headers: headers}`(server streaming)
   def call(_service_mod, rpc, %{channel: channel} = stream, request, opts) do
     {_, {req_mod, req_stream}, {res_mod, response_stream}} = rpc