templates: Fix browsed object metadata availability from javascript
A regression was introduced in 8e0fa87b making browsed object metadata no more available from javascript for anonymous users.
As a consequence, some Jupyter notebooks rendering were broken as some images could not be loaded anymore (see https://archive.softwareheritage.org/browse/origin/content/?origin_url=https://github.com/annotation/tutorials&path=uruk/imagery.ipynb for instance)
Test Plan
A cypress test has been added to check metadata availablity from javascript.
Migrated from D3695 (view on Phabricator)