change to api only handler and remove unused files, bring more structure

internal/utils/utils.go

@@ -0,0 +1,8 @@
+package utils
+
+import "regexp"
+
+func IsValidEmail(email string) bool {
+	re := regexp.MustCompile(`^[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}$`)
+	return re.MatchString(email)
+}