refactor(core): add custom exceptions

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/exception/GmailConfigurationException.java

@@ -0,0 +1,13 @@
+package com.pablotj.restemailbridge.infrastructure.exception;
+
+import java.io.Serial;
+
+public class GmailConfigurationException extends RuntimeException {
+
+    @Serial
+    private static final long serialVersionUID = 1L;
+
+    public GmailConfigurationException(String message) {
+        super(message);
+    }
+}

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/exception/GmailInitializationException.java

@@ -0,0 +1,13 @@
+package com.pablotj.restemailbridge.infrastructure.exception;
+
+import java.io.Serial;
+
+public class GmailInitializationException extends RuntimeException {
+
+    @Serial
+    private static final long serialVersionUID = 1L;
+
+    public GmailInitializationException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/exception/GmailSendErrorException.java

@@ -0,0 +1,14 @@
+package com.pablotj.restemailbridge.infrastructure.exception;
+
+import java.io.Serial;
+
+public class GmailSendErrorException extends RuntimeException {
+
+    @Serial
+    private static final long serialVersionUID = 1L;
+
+    public GmailSendErrorException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+}