As a Wikisource user, I want the credits information to be cached, so that generation of some ebooks. (in cases when the same book is being generated) is more quick and efficient.
Background: Follow-up to T222936. We'd like to eventually cache exported files on disk, but how we go about this will depend on how we implement the job queue (T253283). For now, we can just add simple 10-minute (configurable) caching to the result of all API requests (including those to phetools/credits.py, which is among the slowest bits). First we'll want to switch all API requests to use Symfony's HTTP Client ([insert ticket here]), then we can utilizing its built-in caching.
Acceptance criteria:
- Cache all API requests
- Cache adapter should be configurable, default to the file system
- Cache period should be configurable, default 10 minutes
