client: VolumeListResult: define local type

The `VolumeListResult.Items` field was a `volume.ListResponse`, which
in itself also had two slices (for volumes, and warnings). The Volumes
field contained a slice of pointers to Volumes.

This patch:

- Re-defines `ImageRemoveResult` as a distinct type, containing the
  content of the `volume.ListResponse.Volumes` and `.Warnings`.
- The `VolumeListResult` doesn't use a pointer for the volumes to make
  it slightly easier to deal with (possibly the API type could be
  changed as well, which could allow us to simplify the client code.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

internal/testutil/environment/clean.go

@@ -130,7 +130,7 @@ func deleteAllVolumes(ctx context.Context, t testing.TB, c client.VolumeAPIClien
 	res, err := c.VolumeList(ctx, client.VolumeListOptions{})
 	assert.Check(t, err, "failed to list volumes")
 
-	for _, v := range res.Items.Volumes {
+	for _, v := range res.Items {
 		if _, ok := protectedVolumes[v.Name]; ok {
 			continue
 		}

internal/testutil/environment/protect.go

@@ -231,7 +231,7 @@ func getExistingVolumes(ctx context.Context, t testing.TB, testEnv *Execution) [
 	assert.NilError(t, err, "failed to list volumes")
 
 	var volumes []string
-	for _, vol := range res.Items.Volumes {
+	for _, vol := range res.Items {
 		volumes = append(volumes, vol.Name)
 	}
 	return volumes