Labels: Refactor label entity and cache in label.go and label_cache.go

Signed-off-by: Michael Mayer <michael@photoprism.app>

internal/entity/label_cache_test.go

@@ -0,0 +1,40 @@
+package entity
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFindLabel(t *testing.T) {
+	t.Run("Success", func(t *testing.T) {
+		label := &Label{LabelSlug: "find-me-label", LabelName: "Find Me"}
+
+		if err := label.Save(); err != nil {
+			t.Fatal(err)
+		}
+
+		uncached, findErr := FindLabel("find-me-label", false)
+
+		assert.NoError(t, findErr)
+		assert.Equal(t, "Find Me", uncached.LabelName)
+
+		cached, cacheErr := FindLabel("find-me-label", true)
+
+		assert.NoError(t, cacheErr)
+		assert.Equal(t, "Find Me", cached.LabelName)
+		assert.Equal(t, uncached.LabelSlug, cached.LabelSlug)
+		assert.Equal(t, uncached.ID, cached.ID)
+		assert.Equal(t, uncached.LabelUID, cached.LabelUID)
+	})
+	t.Run("NotFound", func(t *testing.T) {
+		result, err := FindLabel("XXX", true)
+		assert.Error(t, err)
+		assert.NotNil(t, result)
+	})
+	t.Run("EmptyName", func(t *testing.T) {
+		result, err := FindLabel("", true)
+		assert.Error(t, err)
+		assert.NotNil(t, result)
+	})
+}