Add displayVal method to ModelStructureProperty

To serialize value instead of concatenating as if a list.

src/Charcoal/Property/ModelStructureProperty.php

@@ -580,6 +580,36 @@ public function save($val)
         return $val;
     }
 
+    /**
+     * @param  mixed $val     The value to to convert for display.
+     * @param  array $options Optional display options.
+     * @return string
+     */
+    public function displayVal($val, array $options = [])
+    {
+        if ($val === null || $val === '') {
+            return '';
+        }
+
+        /** Parse multilingual values */
+        if ($this['l10n']) {
+            $propertyValue = $this->l10nVal($val, $options);
+            if ($propertyValue === null) {
+                return '';
+            }
+        } elseif ($val instanceof Translation) {
+            $propertyValue = (string)$val;
+        } else {
+            $propertyValue = $val;
+        }
+
+        if (!is_scalar($propertyValue)) {
+            $propertyValue = json_encode($propertyValue, JSON_PRETTY_PRINT);
+        }
+
+        return (string)$propertyValue;
+    }
+
     /**
      * Inject dependencies from a DI Container.
      *