refactor(model): persist date, status, and error description

domain/src/main/java/com/pablotj/restemailbridge/domain/model/Email.java

@@ -1,5 +1,6 @@
 package com.pablotj.restemailbridge.domain.model;
 
+import java.time.Instant;
 import lombok.Builder;
 import lombok.Getter;
 
@@ -7,9 +8,30 @@ import lombok.Getter;
 @Builder
 public class Email {
 
-    private String from;
-    private String to;
-    private String subject;
-    private String body;
+    private final String from;
+    private final String to;
+    private final String subject;
+    private final String body;
+    private EmailStatus status;
+    private final Instant createdAt;
+    private String errorDescription;
 
-}
+    public void markAsSent() {
+        this.status = EmailStatus.SENT;
+    }
+
+    public void markAsFailed(String errorDescription) {
+        this.status = EmailStatus.FAILED;
+        this.errorDescription = errorDescription;
+    }
+
+    public static Email create(String from, String to, String subject, String body) {
+        return Email.builder()
+                .from(from)
+                .to(to)
+                .subject(subject)
+                .body(body)
+                .status(EmailStatus.PENDING)
+                .build();
+    }
+}

domain/src/main/java/com/pablotj/restemailbridge/domain/model/EmailStatus.java

@@ -0,0 +1,5 @@
+package com.pablotj.restemailbridge.domain.model;
+
+public enum EmailStatus {
+    SENT, FAILED, PENDING
+}