allow system variables in footer, loginfooter, welcometext, title2 #6634

Signed-off-by: si458 <simonsmith5521@gmail.com>

common.js

@@ -419,4 +419,20 @@ module.exports.uniqueArray = function (a) {
          }
     }
     return out;
+}
+
+// Replace placeholders in a string with values from an object or a function 
+module.exports.replacePlaceholders = function (template, values) {
+  return template.replace(/\{(\w+)\}/g, (match, key) => {
+    console.log('match', match, 'key', key, 'values', values);
+    if (typeof values === 'function') {
+      return values(key);
+    }
+    else if (values && typeof values === 'object') {
+      return values[key] !== undefined ? values[key] : match;
+    }
+    else {
+      return values !== undefined ? values : match;
+    }
+  });
 }