Use Django caching for explore pages

[jpmckinney]

lib-cove is very slow: open-contracting/lib-cove-oc4ids#23

There is no reason to re-validate the data on each request. This should be cached.

I think we can just use the per-site cache, which is i18n-aware: https://docs.djangoproject.com/en/3.1/topics/cache/#the-per-site-cache Please setup memcached on the server.

[jpmckinney]

@duncandewhurst Please add this to the sprint. It can be done the same for CoVE OCDS and CoVE OC4IDS.

[Bjwebb]

For CoVE OCDS, we have a version switcher on the explore pages, that causes the same url to return different content before/after the switch, so I think we need to be careful how we apply caching (e.g. by putting the version number into the cache key).

[duncandewhurst]

@jpmckinney is this still relevant in respect of the forthcoming work on the frontend?

[jpmckinney]

Yes, caching remains relevant.

[jpmckinney]

Related: #203