Issue #2403485 by larowlan, kim.pepper, idebr, fago: Complete conversion of comment form validation to entity validation

Issue #2230637 by plach, fran seva, yched, swentel: Create a Language field widget and the related formatter

Issue #2355909 by penyaskito, alexpott, Gábor Hojtsy, DuaelFr: language.settings config is not scalable

Issue #2340667 by YesCT, Pedro Lozano, alexpott, martin107: Protect Drupal\Core\Language\Language::id, and use getId().

Issue #2277103 by tim.plunkett, pwolanin, Wim Leers, dawehner, hotpizzas: Switch Drupal::l() and LinkGenerator to expect a Url object.

Issue #2343651 by xjm, tim.plunkett, Wim Leers, dinarcon, dawehner: Remove most remaining l() calls.

Issue #2340251 by iMiksu, alexpott, tim.plunkett, dawehner, Wim Leers: Remove most remaining url() calls.

Issue #2335659 by tim.plunkett, dawehner, effulgentsia, sun: Remove FormState ArrayAccess usage from core.

Issue #2022875 by Berdir, alexpott, Xano, swentel, tim.plunkett, vladan.me: Resolve difference between submitForm(), submit(), and save() in EntityFormController.

Issue #2309323 by Berdir, tim.plunkett: Allow #submit and #validate to be specified as methods of the form object.

Issue #749748 by Bès, penyaskito, sun, hefox, Dave Reid, mavimo | c960657: Fixed Contact, register and comment forms do not prefill with user info from browser.

Issue #2308821 by tim.plunkett: Replace FormErrorInterface with $form_state->setErrorByName() and $form_state->setError().

Issue #2272481 by herom, ParisLiakos, tim.plunkett: Remove usages of watchdog() from forms, plugins and controllers.

Issue #2124957 by Wim Leers, catch: Replace 'content' cache tag with 'rendered' and use it sparingly.

Issue #2228763 by larowlan, alexpott, martin107, jessebeach, xjm: Create a comment-type config entity and use that as comment bundles, require selection in field settings form.

Issue #2246665 by jaredsmith, martin107, YesCT, filijonka, tstoeckler: Typehint with Drupal\Core\Language\LanguageInterface instead Drupal\Core\Language\Language.

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

Issue #2002246 by tompagabor, floretan, lauriii, pakmanlh, rbomhof | pixelite: Capitalize operations links in the comment and taxonomy term admin UI.

Issue #2169361 by plopesc: Convert COMMENT_HIDDEN & COMMENT_CLOSED & COMMENT_OPEN  to a constant on the comment field interface.

Issue #2203407 by nod_, sun: Replace #attached library array values with provider-namespaced strings.

Issue #2002134 by fago, yched, amateescu, effulgentsia: Move TypedData metadata introspection from data objects to definition objects.

Issue #1996238 by sun, nod_, damiankloip, Wim Leers, longwave, alexpott, Xano, mdrummond, Mark Carver, Jeff Burnz, highrockmedia, joelpittet, et al: Replace hook_library_info() by *.libraries.yml file.

Issue #2028025 by David Hernández, Berdir, larowlan, ceng, YesCT, a_thakur: Expand CommentInterface to provide methods.

Issue #2078387 by Xano, andypost, twistor, splatio, InternetDevels, amateescu, Berdir, larowlan, vladan.me: Add an EntityOwnerInterface.

Issue #2164827 by Berdir, Xano, tim.plunkett: Rename the entityInfo() and entityType() methods on EntityInterface and EntityStorageControllerInterface.