Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2512866 by lauriii, Berdir, Wim Leers, Fabianx, effulgentsia, catch, dawehner: CacheContextsManager::optimizeTokens() optimizes ['user', 'user.permissions'] to ['user'] without adding cache tags to invalidate that when the user's roles are modified

Issue #2443323 by Wim Leers, Nitesh Sethia, yched, Fabianx, jhodgdon: New convention: CacheContextInterface implementations should mention their ID in their class-level docblock

Issue #2483781 by borisson_, rbayliss, cilefen, mitalimehta, joshi.rohit100: Move cache contexts classes from \Drupal\Core\Cache to \Drupal\Core\Cache\Context

Issue #2335661 by Wim Leers, pwolanin, dawehner, Fabianx, larowlan, catch, Berdir: Outbound path & route processors must specify cacheability metadata