Issue #2379683 by Gábor Hojtsy: Fix configuration schema issues in contact (indirectly user and system) modules

Issue #2149197 by penyaskito, mikey_p, vijaycs85, herom: Replace format_interval with \Drupal::service('date')->formatInterval().

Issue #2030743 by yingtho, runeasgar, marcingy, YesCT, damiankloip, larowlan, typhonius, dman, areke, Désiré: Improve tests for user form alters in contact module.

Issue #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #950534 by mparker17, mgifford, Mixologic, jbloomfield, erinclerico, theMusician, wmostrey | zirvap: [policy] Consistently use email instead of e-mail in Drupal.

Issue #2223611 by cs_shadow, ACF, dman, visabhishek, vintorezxxi: ContactFormController passed user name field list object to watchdog.

Issue #111702 by mvc, penyaskito, naxoc, jenlampton, montesq: Set fixed "from:" and add "Reply-to:" to improve deliverability of Drupal mail.

Issue #2093027 by Gábor Hojtsy: Fixed Regression: contact category titles not used for page title anymore.

Issue #2074037 by Wim Leers, effulgentsia: Add drupalPostUrl() — drupalPost()/drupalPostAjax() are for forms only, D8 JS performs non-form HTTP requests.

Issue #366950 by amontero, boombatower, brianV, univate, hefox, stpaultim, EllaTheHarpy, babruix: Fixed 'Administer Users' permission should be separate from 'Administer Account Settings'.

Issue #1983548 by Berdir, LukyLuke_ch, giammi, effulgentsia: Convert contact message entities to the new Entity Field API.

Issue #1856556 by Berdir, andypost, das-peter: Convert user contact form into a contact category/bundle.

Issue #1711070 by kid_icarus, tim.plunkett, xjm, droplet, zendoodles and cam8001: Convert tests to use ::$modules property instead of parent::setUp($modules).