PLT-6380 Make team invite links open in the current tab (#6538)

* PLT-6380 Changed link formatting to make team invite links open within the current tab

* Fixed internal link parsing when site URL isn't set

webapp/utils/markdown.jsx

@@ -200,8 +200,15 @@ class MattermostMarkdownRenderer extends marked.Renderer {
 
         output += '" href="' + outHref + '" rel="noreferrer"';
 
-        // special case for channel links and permalinks that are inside the app
-        if (this.formattingOptions.siteURL && new RegExp('^' + TextFormatting.escapeRegex(this.formattingOptions.siteURL) + '\\/[^\\/]+\\/(pl|channels)\\/').test(outHref)) {
+        // special case for team invite links, channel links, and permalinks that are inside the app
+        let internalLink = false;
+        if (this.formattingOptions.siteURL) {
+            const pattern = new RegExp('^' + TextFormatting.escapeRegex(this.formattingOptions.siteURL) + '\\/(?:signup_user_complete|[^\\/]+\\/(?:pl|channels))\\/');
+
+            internalLink = pattern.test(outHref);
+        }
+
+        if (internalLink) {
             output += ' data-link="' + outHref.substring(this.formattingOptions.siteURL) + '"';
         } else {
             output += ' target="_blank"';