test(05-04): add failing tests for attach File, Thumb, and bucket

- ThumbFilename/PartitionDirectory/File.Thumb behavior tests
- OpenBucket fail-loud and memblob tests
- Migrate empty plugin list must create system_files

lagoon/attach/file_test.go

@@ -0,0 +1,19 @@
+package attach
+
+import "testing"
+
+func TestFileTableName(t *testing.T) {
+	if got := (File{}).TableName(); got != "system_files" {
+		t.Fatalf("TableName = %q, want system_files", got)
+	}
+}
+
+func TestFileSelfRegisters(t *testing.T) {
+	for _, m := range All() {
+		switch m.(type) {
+		case *File, File:
+			return
+		}
+	}
+	t.Fatal("File must self-register via attach.Register")
+}