Feat: Fix that Emails render all symbols right

src/main/java/org/dependencytrack/notification/publisher/DefaultNotificationPublishers.java

@@ -25,7 +25,7 @@ public enum DefaultNotificationPublishers {
     SLACK("Slack", "Publishes notifications to a Slack channel", SlackPublisher.class, "/templates/notification/publisher/slack.peb", MediaType.APPLICATION_JSON, true),
     MS_TEAMS("Microsoft Teams", "Publishes notifications to a Microsoft Teams channel", MsTeamsPublisher.class, "/templates/notification/publisher/msteams.peb", MediaType.APPLICATION_JSON, true),
     MATTERMOST("Mattermost", "Publishes notifications to a Mattermost channel", MattermostPublisher.class, "/templates/notification/publisher/mattermost.peb", MediaType.APPLICATION_JSON, true),
-    EMAIL("Email", "Sends notifications to an email address", SendMailPublisher.class, "/templates/notification/publisher/email.peb", MediaType.TEXT_PLAIN, true),
+    EMAIL("Email", "Sends notifications to an email address", SendMailPublisher.class, "/templates/notification/publisher/email.peb", "text/plain; charset=utf-8", true),
     CONSOLE("Console", "Displays notifications on the system console", ConsolePublisher.class, "/templates/notification/publisher/console.peb", MediaType.TEXT_PLAIN, true),
     WEBHOOK("Outbound Webhook", "Publishes notifications to a configurable endpoint", WebhookPublisher.class, "/templates/notification/publisher/webhook.peb", MediaType.APPLICATION_JSON, true),
     CS_WEBEX("Cisco Webex", "Publishes notifications to a Cisco Webex Teams channel", CsWebexPublisher.class, "/templates/notification/publisher/cswebex.peb", MediaType.APPLICATION_JSON, true),

src/main/java/org/dependencytrack/notification/publisher/SendMailPublisher.java

@@ -28,11 +28,15 @@
 import alpine.server.mail.SendMailException;
 import io.pebbletemplates.pebble.PebbleEngine;
 import io.pebbletemplates.pebble.template.PebbleTemplate;
+
+import org.apache.commons.text.StringEscapeUtils;
 import org.dependencytrack.persistence.QueryManager;
 import org.dependencytrack.util.DebugDataEncryption;
 
 import jakarta.json.JsonObject;
 import jakarta.json.JsonString;
+
+import jakarta.ws.rs.core.MediaType;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
@@ -135,13 +139,14 @@ private void sendNotification(final PublishContext ctx, Notification notificatio
             LOGGER.error("Failed to decrypt SMTP password (%s)".formatted(ctx), e);
             return;
         }
+        String unescapedContent = StringEscapeUtils.unescapeHtml4(content);
 
         try {
             final SendMail sendMail = new SendMail()
                     .from(smtpFrom)
                     .to(destinations)
                     .subject(emailSubjectPrefix + " " + notification.getTitle())
-                    .body(content)
+                    .body(mimeType == MediaType.TEXT_HTML ? StringEscapeUtils.escapeHtml4(unescapedContent): unescapedContent)
                     .bodyMimeType(mimeType)
                     .host(smtpHostname)
                     .port(smtpPort)

src/test/java/org/dependencytrack/notification/publisher/DefaultNotificationPublishersTest.java

@@ -72,7 +72,7 @@ public void testEmail() {
         Assert.assertEquals("Sends notifications to an email address", DefaultNotificationPublishers.EMAIL.getPublisherDescription());
         Assert.assertEquals(SendMailPublisher.class, DefaultNotificationPublishers.EMAIL.getPublisherClass());
         Assert.assertEquals("/templates/notification/publisher/email.peb", DefaultNotificationPublishers.EMAIL.getPublisherTemplateFile());
-        Assert.assertEquals(MediaType.TEXT_PLAIN, DefaultNotificationPublishers.EMAIL.getTemplateMimeType());
+        Assert.assertEquals("text/plain; charset=utf-8", DefaultNotificationPublishers.EMAIL.getTemplateMimeType());
         Assert.assertTrue(DefaultNotificationPublishers.EMAIL.isDefaultPublisher());
     }