feat: Add more events for starting and stopping of worker

* When worker is started, then it sends event "started"
* It also sends event "stopped", when it is terminated and
  proces cannot handle message anymore
* This functionality is IMHO important for developers of
  yggdrasil worker. When you develop new worker it is
  important to see that your worker "communication" with
  yggd during start. It is also decency to say something
  like "good bye" at the end.
* Small refactoring of code (do not use numeric constant)
* Updated doc strings
* Extended documentation in com.redhat.Yggdrasil1.Worker1.xml
  according changes in code

internal/work/dispatcher.go

@@ -111,6 +111,7 @@ func (d *Dispatcher) Connect() error {
 	go func() {
 		for s := range signals {
 			log.Tracef("received signal: %#v", s)
+
 			dest, err := d.senderName(dbus.Sender(s.Sender))
 			if err != nil {
 				log.Errorf("cannot find sender: %v", err)

ipc/com.redhat.Yggdrasil1.Worker1.xml

@@ -74,6 +74,16 @@
             3 = WORKING
             Emitted when the worker wishes to continue to announce it is
             working.
+
+            4 = STARTED
+            Emitted when the worker is started, and it is ready
+            to handle received messages. The message_id and response_id are
+            empty.
+
+            5 = STOPPED
+            Emitted when the worker is stopped, and it is not able
+            to handle received messages anymore. The message_id and
+            response_id are also empty.
         -->
         <signal name="Event">
             <arg type="u" name="name" />

ipc/interfaces.go

@@ -2,6 +2,7 @@ package ipc
 
 import (
 	_ "embed"
+	"fmt"
 )
 
 //go:embed com.redhat.Yggdrasil1.Dispatcher1.xml
@@ -12,13 +13,16 @@ var InterfaceDispatcher string
 type DispatcherEvent uint
 
 const (
-	// Emitted when the dispatcher receives the "disconnect" command.
+	// DispatcherEventReceivedDisconnect is emitted when the dispatcher receives
+	// the "disconnect" command.
 	DispatcherEventReceivedDisconnect DispatcherEvent = 1
 
-	// Emitted when the transport unexpected disconnects from the network.
+	// DispatcherEventUnexpectedDisconnect is emitted when the transport unexpected
+	// disconnects from the network.
 	DispatcherEventUnexpectedDisconnect DispatcherEvent = 2
 
-	// Emitted when the transport reconnects to the network.
+	// DispatcherEventConnectionRestored is emitted when the transport reconnects
+	// to the network.
 	DispatcherEventConnectionRestored DispatcherEvent = 3
 )
 
@@ -29,28 +33,40 @@ type WorkerEventName uint
 
 const (
 
-	// Emitted when the worker "accepts" a dispatched message and begins
-	// "working".
+	// WorkerEventNameBegin is emitted when the worker "accepts"
+	// a dispatched message and begins "working".
 	WorkerEventNameBegin WorkerEventName = 1
 
-	// Emitted when the worker finishes "working".
+	// WorkerEventNameEnd is emitted when the worker finishes "working".
 	WorkerEventNameEnd WorkerEventName = 2
 
-	// Emitted when the worker wishes to continue to announce it is
-	// working.
+	// WorkerEventNameWorking is emitted when the worker wishes
+	// to continue to announce it is working.
 	WorkerEventNameWorking WorkerEventName = 3
+
+	// WorkerEventNameStarted is emitted when worker finished starting
+	// process, and it can start process received messages.
+	WorkerEventNameStarted WorkerEventName = 4
+
+	// WorkerEventNameStopped is emitted when worker is stopped,
+	// and it cannot process any message.
+	WorkerEventNameStopped WorkerEventName = 5
 )
 
 func (e WorkerEventName) String() string {
 	switch e {
-	case 1:
+	case WorkerEventNameBegin:
 		return "BEGIN"
-	case 2:
+	case WorkerEventNameEnd:
 		return "END"
-	case 3:
+	case WorkerEventNameWorking:
 		return "WORKING"
+	case WorkerEventNameStarted:
+		return "STARTED"
+	case WorkerEventNameStopped:
+		return "STOPPED"
 	}
-	return ""
+	return fmt.Sprintf("UNKNOWN (value: %d)", e)
 }
 
 type WorkerEvent struct {

worker/worker.go

@@ -125,6 +125,17 @@ func (w *Worker) Connect(quit <-chan os.Signal) error {
 		return fmt.Errorf("request name failed")
 	}
 
+	// Emit a started event
+	err = w.EmitEvent(
+		ipc.WorkerEventNameStarted,
+		"",
+		"",
+		map[string]string{},
+	)
+	if err != nil {
+		return fmt.Errorf("cannot emit event: %w", err)
+	}
+
 	signals := make(chan *dbus.Signal)
 	w.conn.Signal(signals)
 	go func() {
@@ -142,6 +153,17 @@ func (w *Worker) Connect(quit <-chan os.Signal) error {
 
 	<-quit
 
+	// Emit a stopped event
+	err = w.EmitEvent(
+		ipc.WorkerEventNameStopped,
+		"",
+		"",
+		map[string]string{},
+	)
+	if err != nil {
+		return fmt.Errorf("cannot emit event: %w", err)
+	}
+
 	return nil
 }