Initialize JinjaOptions right after app creation.

Starting from Flask>=1.0, some of plain `app` properties were
rewritten as property descriptors, so setting them may accidentialy
initialize JinjaEnvironment. After this point jinja2 won't notice
any change to `jinja_options`. So I reordered assignment in app
initialization and now `jinja_options` added firstly.

ckan/config/middleware/flask_app.py

@@ -82,6 +82,15 @@ def make_flask_stack(conf, **app_conf):
     debug = asbool(conf.get('debug', conf.get('DEBUG', False)))
     testing = asbool(app_conf.get('testing', app_conf.get('TESTING', False)))
     app = flask_app = CKANFlask(__name__)
+    # Set jinja_options as soon as possible as it won't affect
+    # tempaltes in any way after JinjaEnvironment created. It may be
+    # not obvious, but some of `app` properties are implemented as
+    # property descriptors, so even assigning can implicitly create
+    # JinjaEnvironment.
+    #
+    # https://flask.palletsprojects.com/en/1.1.x/api/#flask.Flask.jinja_options
+    app.jinja_options = jinja_extensions.get_jinja_env_options()
+
     app.debug = debug
     app.testing = testing
     app.template_folder = os.path.join(root, 'templates')