db: add tests for two factors (#6099)

* Rename to TwoFactors.Create

* Use GORM to execute queries

* TwoFactor.GetByUserID

* Add tests

* Fix failing tests

* Add MD5 tests

* Add tests for RandomChars

internal/strutil/strutil_test.go

@@ -41,3 +41,17 @@ func TestToUpperFirst(t *testing.T) {
 		})
 	}
 }
+
+func TestRandomChars(t *testing.T) {
+	cache := make(map[string]bool)
+	for i := 0; i < 100; i++ {
+		chars, err := RandomChars(10)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if cache[chars] {
+			t.Fatalf("Duplicated chars %q", chars)
+		}
+		cache[chars] = true
+	}
+}