feat(email): add email service and configuration for sending emails

backend/src/main/java/de/szut/casino/CasinoApplication.java

@@ -8,6 +8,10 @@ import org.springframework.boot.CommandLineRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.Bean;
+import org.springframework.mail.MailException;
+import org.springframework.mail.MailSender;
+import org.springframework.mail.SimpleMailMessage;
+import org.springframework.mail.javamail.JavaMailSenderImpl;
 import org.springframework.web.client.RestTemplate;
 
 import java.math.BigDecimal;
@@ -26,6 +30,11 @@ public class CasinoApplication {
         return new RestTemplate();
     }
 
+    @Bean
+    public static JavaMailSenderImpl javaMailSenderImpl() {
+        return new JavaMailSenderImpl();
+    }
+
     @Bean
     public CommandLineRunner initData(LootBoxRepository lootBoxRepository, RewardRepository rewardRepository) {
         return _ -> {

backend/src/main/java/de/szut/casino/health/HealthController.java

@@ -1,5 +1,8 @@
 package de.szut.casino.health;
 
+import de.szut.casino.security.service.EmailService;
+import de.szut.casino.user.UserEntity;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RestController;
 
@@ -8,8 +11,17 @@ import java.util.Map;
 @RestController
 public class HealthController {
 
+    @Autowired
+    private EmailService emailService;
+
     @GetMapping("/health")
     public Map<String, String> healthCheck() {
+        UserEntity user = new UserEntity();
+        user.setEmail("user@mail.com");
+        user.setUsername("user");
+
+        this.emailService.sendRegistrationEmail(user);
+
         return Map.of("status", "UP");
     }
 }

backend/src/main/java/de/szut/casino/security/service/EmailService.java

@@ -0,0 +1,48 @@
+package de.szut.casino.security.service;
+
+import de.szut.casino.user.UserEntity;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.mail.SimpleMailMessage;
+import org.springframework.mail.javamail.JavaMailSenderImpl;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+@Service
+public class EmailService {
+    private JavaMailSenderImpl mailSender;
+
+    private MailConfig mailConfig;
+
+    public EmailService(JavaMailSenderImpl mailSender, MailConfig mailConfig) {
+        try {
+            this.mailSender = mailSender;
+            this.mailConfig = mailConfig;
+            this.mailSender.setHost(mailConfig.host);
+            this.mailSender.setPort(mailConfig.port);
+            if (mailConfig.authenticationEnabled) {
+                this.mailSender.setUsername(mailConfig.username);
+                this.mailSender.setPassword(mailConfig.password);
+            }
+        } catch (Exception e) {
+            System.out.println(e.getMessage());
+        }
+    }
+
+    public void sendRegistrationEmail(UserEntity user) {
+        String body = "Hallo " + user.getUsername() + ",\n\nA Willkommen bei Trustworthy Casino©! Wir freuen uns, Sie an Bord zu haben.\n\n";
+        SimpleMailMessage mail = new SimpleMailMessage();
+
+        mail.setFrom(mailConfig.fromAddress);
+        mail.setSubject("Willkommen bei Trustworthy Casino©");
+        mail.setTo(user.getEmail());
+        mail.setText(body);
+
+        sendEmail(mail);
+    }
+
+    private void sendEmail(SimpleMailMessage mail) {
+        this.mailSender.send(mail);
+    }
+}

backend/src/main/java/de/szut/casino/security/service/MailConfig.java

@@ -0,0 +1,25 @@
+package de.szut.casino.security.service;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+@Service
+public class MailConfig {
+    @Value("${app.mail.host}")
+    public String host;
+
+    @Value("${app.mail.port}")
+    public Integer port;
+
+    @Value("${app.mail.authentication}")
+    public Boolean authenticationEnabled;
+
+    @Value("${app.mail.username}")
+    public String username;
+
+    @Value("${app.mail.password}")
+    public String password;
+
+    @Value("${app.mail.from-address}")
+    public String fromAddress;
+}