fix gravatar url is invalid when email contains upper characters

pkg/utils/avatar_test.go

@@ -0,0 +1,14 @@
+package utils
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetGravatarUrl(t *testing.T) {
+	// Reference: https://en.gravatar.com/site/implement/hash/
+	expectedValue := "https://www.gravatar.com/avatar/0bc83cb571cd1c50ba6f3e8a78ef1346"
+	actualValue := GetGravatarUrl("MyEmailAddress@example.com")
+	assert.Equal(t, expectedValue, actualValue)
+}