EasyCache 7.0.0 - OXID 7.0-7.5 (Twig)

First public release for OXID 7. The major version matches the OXID major it targets, so this is
the 7.x line; 6.x covers OXID 6 in parallel.

Added

• A file-based full-page cache: whitelisted storefront pages are stored as finished HTML and
  served on later requests without running the controller action or the template render again.
• Tag-based invalidation. Cached pages are filed under the products, categories, manufacturers
  and content pages they actually show, so a single article change clears exactly the pages that
  displayed it instead of the whole cache.
• Automatic purge when an article sells out, hooked into OXID's own Article::onChange() - which
  also fires during checkout, when stock is reduced.
• Optional gzip storage and optional whitespace-only HTML minification, both togglable without
  clearing the cache. Minification uses voku/html-min, kept as a suggested rather than a
  required dependency; without it the setting stays inert and the backend says so.
• Per-controller statistics - hits, misses, hit ratio and average response time per view class -
  with a backend page to read and reset them. Off by default, because it costs a write per
  request.
• X-EasyCache and X-EasyCache-Timing response headers on every request, carrying HIT,
  MISS or BYPASS plus a timing breakdown. Deliberately low cardinality, so they can be
  aggregated at a CDN or in log analysis without parsing anything apart.
• A backend settings page for the master switch, the TTL, the controller whitelist and the gzip,
  minify and statistics toggles.
• A backend cache page to clear everything, clear the start page, or clear the pages belonging to
  one product, category or manufacturer found by name.
• foun10:easycache:clear, the same clear the backend button runs, for use from cron.
• Session ids and CSRF tokens are replaced with placeholders before a page is stored and
  re-injected from the current visitor's own session when it is served, so no visitor is ever
  handed another visitor's token.
• A deny-all .htaccess written into the cache directory on first use, because that directory
  sits inside the document root.

Fixed

• foun10:easycache:clear cleared the cache and then died with a TypeError and exit code 255,
  because execute() returned void where Symfony Console requires an int. A nightly cron
  would have mailed a fatal every night despite having done its job.
• Session values were passed to str_replace() unchecked. On OXID 7 Session::getId() returns
  null when no session was started, which raised a TypeError under strict_types and took
  the whole page down on the first cache write.

Known limitations

• Only guests are cached. As soon as a visitor logs in or puts something in the basket, every
  page renders live. On a shop where most traffic is logged in, the benefit will be small.
• This is not a reverse proxy. A cache hit is still a full PHP request - the shop boots, the
  session is resolved and the view object initialises before the stored HTML is returned. It
  skips the render, not the framework.
• The start page belongs to no single product or category, so it carries one fixed tag and is
  cleared only by TTL, by hand, or by the nightly job.
• Cached HTML is exactly what was rendered. Anything that must differ per visitor has to be
  loaded client-side, or its page kept off the whitelist.