Issue #2760167 by kim.pepper, markcarver, jibran, dawehner, znerol, Wim Leers, larowlan, xjm, tim.plunkett: Add \Drupal\Core\Messenger\Messenger

Issue #2278383 by dawehner, Xano, kim.pepper, twistor, jibran, Jo Fitzgerald, joelpittet, pritish.kumar, Fabianx, Crell, larowlan, alexpott, catch, Wim Leers: Create an injectible service for drupal_set_message()

Revert "Issue #2278383 by Xano, dawehner, kim.pepper, twistor, joelpittet, Fabianx, Crell, jibran, alexpott, Wim Leers: Create an injectible service for drupal_set_message()"

This reverts commit ee222725.

Issue #2278383 by Xano, dawehner, kim.pepper, twistor, joelpittet, Fabianx, Crell, jibran, alexpott, Wim Leers: Create an injectible service for drupal_set_message()

Revert "Issue #2403307 by dawehner, marthinal, tedbow, clemens.tolboom, Wim Leers, neclimdul, Crell, klausi, andypost, e0ipso: RPC endpoints for user authentication: log in, check login status, log out"

This reverts commit 18feefc3.

Issue #2403307 by dawehner, marthinal, tedbow, clemens.tolboom, Wim Leers, neclimdul, Crell, klausi, andypost, e0ipso: RPC endpoints for user authentication: log in, check login status, log out