jsonify template tag added

Closes #5866

src/cmsplugin_blurp/templatetags/blurp_tags.py

@@ -1,8 +1,13 @@
 import logging
+import json
 
 from django import template
 from django.conf import settings
 from django.utils.html import escape
+from django.core.serializers import serialize
+from django.core.serializers.json import DjangoJSONEncoder
+from django.db.models.query import QuerySet
+from django.utils.safestring import mark_safe
 
 from classytags.arguments import Argument
 from classytags.core import Options, Tag
@@ -11,6 +16,14 @@ from .. import utils
 
 register = template.Library()
 
+# originally copied from django-jsonify(https://bitbucket.org/marltu/django-jsonify/)
+# released under a three-clause BSD License by Marius Grigaitis
+@register.filter
+def jsonify(obj):
+    if isinstance(obj, QuerySet):
+        return mark_safe(serialize('json', obj))
+    return mark_safe(json.dumps(obj, cls=DjangoJSONEncoder))
+
 @register.tag
 class RenderBlurp(Tag):
     name = 'render_blurp'