Restrict context var override on package page & support timezone and language query params
Users can (accidentally) override context vars with query params.
This may lead to issues when rendering templates (e.g. comments=...
).
Fixes aurweb-errors#534
Support setting the timezone as well as the language via query params:
- The timezone parameter previously only worked on certain pages. Now it's working globally.
- While we're at it, let's also add the language as a possible parameter.
- Refactor: Combine all code for the timestamp and language logic into their respective functions.
- Remove unused AURTZ cookie.
- Add test code to cover all scenarios.