Provide client and service loader files

The service also includes a service info helper class that
    can wrap requests and extract execution context of request.
    This includes the vagrant service endpoint for connecting
    a client back to the service and the scope of the request.
    It also provides a helper for creating and reusing clients.

plugins/commands/serve/client.rb

@@ -0,0 +1,13 @@
+module VagrantPlugins
+  module CommandServe
+    module Client
+      # Simple alias
+      SDK = Service::SDK
+      SRV = Service::SRV
+      ServiceInfo = Service::ServiceInfo
+
+      autoload :Machine, Vagrant.source_root.join("plugins/commands/serve/client/machine").to_s
+      autoload :Terminal, Vagrant.source_root.join("plugins/commands/serve/client/terminal_client").to_s
+    end
+  end
+end

plugins/commands/serve/service.rb

@@ -0,0 +1,83 @@
+module VagrantPlugins
+  module CommandServe
+    module Service
+      # Simple aliases
+      SDK = Hashicorp::Vagrant::Sdk
+      SRV = Hashicorp::Vagrant
+
+      autoload :CommandService, Vagrant.source_root.join("plugins/commands/serve/service/command_service").to_s
+      autoload :HostService, Vagrant.source_root.join("plugins/commands/serve/service/host_service").to_s
+      autoload :InternalService, Vagrant.source_root.join("plugins/commands/serve/service/internal_service").to_s
+      autoload :ProviderService, Vagrant.source_root.join("plugins/commands/serve/service/provider_service").to_s
+
+      class ServiceInfo
+        class ClientInterceptor < GRPC::ClientInterceptor
+          def request_response(request:, call:, method:, metadata: {})
+            metadata["client-version"] = "Vagrant/#{Vagrant::VERSION}"
+            metadata["client-api-protocol"] = "1,1"
+            yield
+          end
+        end
+
+        # @return [String, nil] Resource ID for basis of request
+        attr_reader :basis
+        # @return [String, nil] Resource ID for project of request
+        attr_reader :project
+        # @return [String, nil] Resource ID for machine of request
+        attr_reader :machine
+        # @return [String, nil] GRPC endpoint for the Vagrant service
+        attr_reader :vagrant_service_endpoint
+        # @return [String] Name of requested plugin
+        attr_reader :plugin_name
+
+        CLIENT_LOCK = Mutex.new
+
+        def initialize(basis: nil, project: nil, machine: nil, vagrant_service_endpoint: nil, plugin_name: nil)
+          @basis = basis
+          @project = project
+          @machine = machine
+          @vagrant_service_endpoint = vagrant_service_endpoint
+          @plugin_name = plugin_name
+        end
+
+        def self.info
+          info = Thread.current.thread_variable_get(:service_info)
+          if info.nil?
+            raise ArgumentError,
+              "Service information has not been set!"
+          end
+          info
+        end
+
+        def self.client_for(service)
+          CLIENT_LOCK.synchronize do
+            @clients ||= {}
+            return @clients[service] if @clients[service]
+            @clients[service] = service::Stub.new(
+              info.vagrant_service_endpoint,
+              :this_channel_is_insecure,
+              interceptors: [ClientInterceptor.new]
+            )
+          end
+        end
+
+        def self.with_info(context)
+          info = new(
+            basis: context.metadata["basis_resource_id"],
+            project: context.metadata["project_resource_id"],
+            machine: context.metadata["machine_resource_id"],
+            vagrant_service_endpoint: context.metadata["vagrant_service_endpoint"],
+            plugin_name: context.metadata["plugin_name"],
+          )
+          Thread.current.thread_variable_set(:service_info, info)
+          return if !block_given?
+          begin
+            yield info
+          ensure
+            Thread.current.thread_variable_set(:service_info, nil)
+          end
+        end
+      end
+    end
+  end
+end