Reduce notification nesting, at 'continue' result

Co-authored-by: Ulf Wiger <ulf@wiger.net>
Reviewed-on: #2

rebar.config

@@ -3,7 +3,7 @@
 {plugins, [rebar3_hex]}.
 {deps, [
          {gmserialization, {git, "https://git.qpq.swiss/QPQ-AG/gmserialization.git",
-                            {ref, "bff07885fb"}}}
+                            {ref, "ac64e01b0f"}}}
        ]}.
 
 {xref_checks, [undefined_function_calls, undefined_functions,

rebar.lock

@@ -8,5 +8,5 @@
   1},
  {<<"gmserialization">>,
   {git,"https://git.qpq.swiss/QPQ-AG/gmserialization.git",
-       {ref,"bff07885fb9fd328db4d1ae2cd27b118b57dd929"}},
+       {ref,"ac64e01b0f675c1a34c70a827062f381920742db"}},
   0}].

src/gmmpp_msgs.erl

@@ -150,7 +150,7 @@ decode(MsgBin, ?PROTOCOL_JSON, Vsn) ->
                 #{ <<"method">>  := Method
                  , <<"params">>  := Params } ->
                     %% JSON-RPC notification
-                    #{ notification => #{ msg => validate(decode_msg_(Method, Params), Vsn) }};
+                    #{ notification => validate(decode_msg_(Method, Params), Vsn) };
                 #{ <<"id">> := Id
                  , <<"result">> := Result } ->
                     #{ reply => #{ id => Id
@@ -167,7 +167,7 @@ decode(MsgBin, ?PROTOCOL_JSON, Vsn) ->
 encode(#{call := Req0}, P, V) ->
     {Id, Req} = maps:take(id, Req0),
     encode_request(Req, Id, P, V);
-encode(#{notification := #{msg := Msg}}, P, V) ->
+encode(#{notification := Msg}, P, V) ->
     encode_msg(Msg, P, V);
 encode(#{reply := Reply0}, P, V) when is_map(Reply0) ->
     {Id, Reply} = maps:take(id, Reply0),
@@ -204,7 +204,11 @@ encode_reply(Reply, Id, ?PROTOCOL_JSON, _Vsn) ->
               ok ->
                   #{ <<"jsonrpc">> => <<"2.0">>
                    , <<"id">>      => Id
-                   , <<"result">>  => <<"ok">> }
+                   , <<"result">>  => <<"ok">> };
+              continue ->
+                  #{ <<"jsonrpc">> => <<"2.0">>
+                   , <<"id">>      => Id
+                   , <<"result">>  => <<"continue">> }
           end,
     json_encode(Msg).
 
@@ -231,6 +235,7 @@ error_code(unknown_method   ) -> -32601;
 error_code(_                ) -> -32603.   % internal error
 
 decode_result(<<"ok">>, _) -> ok;
+decode_result(<<"continue">>, _) -> continue;
 decode_result(#{<<"connect_ack">> := #{ <<"protocol">> := P
                                       , <<"version">>  := V }}, Vsn) ->
     Msg = #{connect_ack => #{ protocol => P