feat: support service.command

This patch extends dcmerge to support the command attribut of a defined service.
For example:

```yaml
services:
  busybox
    command: [ "/usr/bin/cp", "--recursive", "--force", "/tmp/bar.txt", "/tmp/foo.txt"]
    image: library/busybox:latest
```

The command attribute is interpreted as a whole. This means that individual
arguments are not merged as a comparison, as this would change the meaning of
the command attribute.

pkg/domain/dockerCompose/config.go

@@ -531,6 +531,7 @@ func NewSecret() *Secret {
 }
 
 type Service struct {
+	Command            []string                   `json:"command,omitempty" yaml:"command,omitempty"`
 	CapabilitiesAdd    []string                   `json:"cap_add,omitempty" yaml:"cap_add,omitempty"`
 	CapabilitiesDrop   []string                   `json:"cap_drop,omitempty" yaml:"cap_drop,omitempty"`
 	DependsOnContainer *DependsOnContainer        `json:"depends_on,omitempty" yaml:"depends_on,omitempty"`
@@ -641,7 +642,8 @@ func (s *Service) Equal(equalable Equalable) bool {
 	case s == nil && service != nil:
 		return false
 	default:
-		return equalSlice(s.CapabilitiesAdd, service.CapabilitiesAdd) &&
+		return equalSlice(s.Command, service.Command) &&
+			equalSlice(s.CapabilitiesAdd, service.CapabilitiesAdd) &&
 			equalSlice(s.CapabilitiesDrop, service.CapabilitiesDrop) &&
 			s.DependsOnContainer.Equal(service.DependsOnContainer) &&
 			s.Deploy.Equal(service.Deploy) &&
@@ -673,6 +675,7 @@ func (s *Service) MergeExistingWin(service *Service) {
 	// 	fallthrough
 
 	default:
+		s.mergeExistingWinCommand(service.Command)
 		s.mergeExistingWinCapabilitiesAdd(service.CapabilitiesAdd)
 		s.mergeExistingWinCapabilitiesDrop(service.CapabilitiesDrop)
 		s.mergeExistingWinDependsOnContainer(service.DependsOnContainer)
@@ -707,6 +710,7 @@ func (s *Service) MergeLastWin(service *Service) {
 	// 	fallthrough
 
 	default:
+		s.mergeLastWinCommand(service.Command)
 		s.mergeLastWinCapabilitiesAdd(service.CapabilitiesAdd)
 		s.mergeLastWinCapabilitiesDrop(service.CapabilitiesDrop)
 		s.mergeLastWinDependsOnContainer(service.DependsOnContainer)
@@ -723,6 +727,13 @@ func (s *Service) MergeLastWin(service *Service) {
 	}
 }
 
+func (s *Service) mergeExistingWinCommand(command []string) {
+	if len(s.Command) > 0 {
+		return
+	}
+	s.Command = command
+}
+
 func (s *Service) mergeExistingWinCapabilitiesAdd(capabilitiesAdd []string) {
 	for _, capabilityAdd := range capabilitiesAdd {
 		if !existsInSlice(s.CapabilitiesAdd, capabilityAdd) && len(capabilityAdd) > 0 {
@@ -935,6 +946,12 @@ func (s *Service) mergeExistingWinVolumes(volumes []string) {
 	}
 }
 
+func (s *Service) mergeLastWinCommand(command []string) {
+	if len(command) > 0 {
+		s.Command = command
+	}
+}
+
 func (s *Service) mergeLastWinCapabilitiesAdd(capabilitiesAdd []string) {
 	for _, capabilityAdd := range capabilitiesAdd {
 		if len(capabilityAdd) <= 0 {