Add mappers for loading command client

plugins/commands/serve/mappers/command.rb

@@ -17,6 +17,38 @@ module VagrantPlugins
           SDK::Command::Arguments.decode(proto.value.value)
         end
       end
+
+      class CommandProtoFromSpec < Mapper
+        def initialize
+          super(
+            inputs: [Input.new(type: SDK::FuncSpec::Value) { |arg|
+                arg.type == "hashicorp.vagrant.sdk.Args.Command" &&
+                  !arg&.value&.value.nil?
+              }
+            ],
+            output: SDK::Args::Command,
+            func: method(:converter)
+          )
+        end
+
+        def converter(fv)
+          SDK::Args::Command.decode(fv.value.value)
+        end
+      end
+
+      class CommandFromProto < Mapper
+        def initialize
+          inputs = [].tap do |i|
+            i << Input.new(type: SDK::Args::Command)
+            i << Input.new(type: Broker)
+          end
+          super(inputs: inputs, output: Client::Command, func: method(:converter))
+        end
+
+        def converter(proto, broker)
+          Client::Command.load(proto, broker: broker)
+        end
+      end
     end
   end
 end