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_test.go

@@ -301,6 +301,7 @@ func TestService_Equal(t *testing.T) {
 		},
 		{
 			equalableA: &dockerCompose.Service{
+				Command:            []string{},
 				CapabilitiesAdd:    []string{},
 				CapabilitiesDrop:   []string{},
 				DependsOnContainer: &dockerCompose.DependsOnContainer{},
@@ -316,6 +317,7 @@ func TestService_Equal(t *testing.T) {
 				Volumes:            []string{},
 			},
 			equalableB: &dockerCompose.Service{
+				Command:            []string{},
 				CapabilitiesAdd:    []string{},
 				CapabilitiesDrop:   []string{},
 				DependsOnContainer: &dockerCompose.DependsOnContainer{},
@@ -332,6 +334,15 @@ func TestService_Equal(t *testing.T) {
 			},
 			expectedResult: true,
 		},
+		{
+			equalableA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			equalableB: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			expectedResult: true,
+		},
 		{
 			equalableA: &dockerCompose.Service{
 				CapabilitiesAdd: []string{"NET_ADMIN"},
@@ -636,6 +647,52 @@ func TestService_MergeExistingWin(t *testing.T) {
 			expectedService:    &dockerCompose.Service{},
 		},
 
+		// Command
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{""},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+
 		// CapabilitiesAdd
 		{
 			serviceDeploymentA: &dockerCompose.Service{
@@ -1620,6 +1677,52 @@ func TestService_MergeLastWin(t *testing.T) {
 			expectedService:    &dockerCompose.Service{},
 		},
 
+		// Command
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+		},
+		{
+			serviceDeploymentA: &dockerCompose.Service{
+				Command: []string{"/usr/bin/cp", "--recursive", "/tmp/foo.txt", "/tmp/bar.txt"},
+			},
+			serviceDeploymentB: &dockerCompose.Service{
+				Command: []string{""},
+			},
+			expectedService: &dockerCompose.Service{
+				Command: []string{""},
+			},
+		},
+
 		// CapabilitiesAdd
 		{
 			serviceDeploymentA: &dockerCompose.Service{