Refactoring + migrate mail package to server.

backend/server/src/main/resources/application.yml

@@ -17,6 +17,19 @@ spring:
       hibernate:
         format_sql: true
 
+  mail:
+    host: smtp.resend.com
+    port: 587
+    username: resend
+    password: re_JnLD5ndg_GnKtXcTqskXm1bg7Wxnghna3
+    properties:
+      mail:
+        smtp:
+          auth: true
+          starttls:
+            enable: true
+    default-encoding: UTF-8
+
 eureka:
   client:
     service-url: