Replace pprint with saneyaml.dump for SSVC decision tree display

vulnerabilities/templates/advisory_detail.html

@@ -4,6 +4,7 @@
 {% load static %}
 {% load show_cvss %}
 {% load url_filters %}
+{% load utils %}
 
 {% block title %}
 VulnerableCode Advisory Details - {{ advisory.advisory_id }}
@@ -583,7 +584,7 @@
                             <summary class="is-size-7 has-text-link" style="cursor: pointer;">
                               View SSVC decision tree
                             </summary>
-                            <pre>{{ ssvc.options|pprint }}</pre>
+                            <pre>{{ ssvc.options|yaml_dump }}</pre>
                           </details>
                         </div>
                     </div>

vulnerabilities/templatetags/utils.py

@@ -10,6 +10,7 @@
 
 from aboutcode.pipeline import humanize_time
 from django import template
+import saneyaml
 
 register = template.Library()
 
@@ -39,3 +40,14 @@ def active_item(context, url_name):
 @register.filter
 def get_item(dictionary, key):
     return dictionary.get(key)
+
+
+@register.filter
+def yaml_dump(value):
+    """Render structured data as YAML using saneyaml.dump."""
+    if value is None:
+        return ""
+    try:
+        return saneyaml.dump(value)
+    except (TypeError, ValueError):
+        return str(value)