fix: Relative links in document HTML should become absolute in emailed snippets

closes #6480

server/models/helpers/DocumentHelper.tsx

@@ -30,6 +30,8 @@ type HTMLOptions = {
    * number then the urls will be signed for that many seconds. (defaults to false)
    */
   signedUrls?: boolean | number;
+  /** The base URL to use for relative links */
+  baseUrl?: string;
 };
 
 @trace()
@@ -111,6 +113,7 @@ export default class DocumentHelper {
       includeStyles: options?.includeStyles,
       includeMermaid: options?.includeMermaid,
       centered: options?.centered,
+      baseUrl: options?.baseUrl,
     });
 
     addTags({

server/models/helpers/ProsemirrorHelper.tsx

@@ -23,6 +23,8 @@ export type HTMLOptions = {
   includeMermaid?: boolean;
   /** Whether to include styles to center diff (defaults to true) */
   centered?: boolean;
+  /** The base URL to use for relative links */
+  baseUrl?: string;
 };
 
 type MentionAttrs = {
@@ -217,6 +219,16 @@ export default class ProsemirrorHelper {
       target
     );
 
+    // Convert relative urls to absolute
+    if (options?.baseUrl) {
+      const elements = doc.querySelectorAll("a[href]");
+      for (const el of elements) {
+        if ("href" in el && (el.href as string).startsWith("/")) {
+          el.href = new URL(el.href as string, options.baseUrl).toString();
+        }
+      }
+    }
+
     // Inject mermaidjs scripts if the document contains mermaid diagrams
     if (options?.includeMermaid) {
       const mermaidElements = dom.window.document.querySelectorAll(