Add idempotent object deletion

internal/adapters/storage/fake.go

@@ -23,11 +23,13 @@ type FakeBackend struct {
 	Uploads    []FakeUploadCall
 	Downloads  []FakeDownloadCall
 	Reads      []FakeReadCall
+	Deletes    []string
 	ExistsKeys []string
 
 	ListErr      error
 	DownloadErr  error
 	UploadErr    error
+	DeleteErr    error
 	ExistsErr    error
 	UploadHook   func(FakeUploadCall) error
 	DownloadHook func(FakeDownloadCall) error
@@ -316,6 +318,25 @@ func fakeObjectETag(data []byte) string {
 	return hex.EncodeToString(sum[:])
 }
 
+// Delete removes one object. Removing an absent object succeeds.
+func (f *FakeBackend) Delete(ctx context.Context, key string) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	if f.DeleteErr != nil {
+		return f.DeleteErr
+	}
+	normalizedKey := normalizeObjectKey(key)
+	if normalizedKey == "" {
+		return fmt.Errorf("delete object: key is required")
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.Deletes = append(f.Deletes, normalizedKey)
+	delete(f.Objects, normalizedKey)
+	return nil
+}
+
 // Exists checks object presence.
 func (f *FakeBackend) Exists(ctx context.Context, key string) (bool, error) {
 	if err := ctx.Err(); err != nil {