[anoziere]

Declares /api/header-highlights to the shared cache of the public pages added by thelia/thelia#4148. A page that reads the highlights can now be kept by the proxy, tagged header_highlights, and saving or deleting a highlight or its image purges that key.

• SharedCache/HeaderHighlightsSharedCache implements Thelia\Core\SharedCache\SharedCacheContributorInterface.
• SharedCache/HeaderHighlightsPurgeListener purges on the Propel post save and post delete events of the four tables, which every write of the configuration screen goes through.
• Both are registered only when the core has the interface, so on an older core the module behaves as before.
• Integration test in Tests/Integration, run from the shop root after php bin/test-prepare with vendor/bin/phpunit -c local/modules/HeaderHighlights.
• Version 2.2.0.

Needs the release of thelia/core that contains thelia/thelia#4148 (SharedCacheContributorInterface and SharedCacheInvalidator are not in 3.2.3): merge after it.

Seen while testing, not changed here: the configuration screen cannot save a block that has no image yet (the insert into header_highlights_image fails on the required file column), and a highlight saved without a call to action breaks every front page (null text given to the button component).