add smtp, finish redis and register(with invitation code and verification code)

Change-Id: Ie8e07fe058b9d970a00424d463ce30d4ec72086a
diff --git a/src/main/java/com/example/g8backend/util/mailUtil.java b/src/main/java/com/example/g8backend/util/mailUtil.java
new file mode 100644
index 0000000..5c8ad55
--- /dev/null
+++ b/src/main/java/com/example/g8backend/util/mailUtil.java
@@ -0,0 +1,24 @@
+package com.example.g8backend.util;
+
+import org.springframework.mail.SimpleMailMessage;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.stereotype.Component;
+
+@Component
+public class mailUtil {
+
+    private final JavaMailSender javaMailSender;
+
+    public mailUtil(JavaMailSender javaMailSender) {
+        this.javaMailSender = javaMailSender;
+    }
+
+    public void sendMail(String to, String subject, String message) {
+        SimpleMailMessage mail = new SimpleMailMessage();
+        mail.setFrom("2038234690@qq.com");
+        mail.setTo(to);
+        mail.setSubject(subject);
+        mail.setText(message);
+        javaMailSender.send(mail);
+    }
+}