[MERGE] forward port branch 9.0 up to 3805eb62

addons/account/models/account_invoice.py

addons/account/models/account_move.py

addons/account/models/partner.py

addons/account/views/account_view.xml

addons/auth_oauth/ir_configparameter.py

addons/calendar/calendar.py

addons/event_sale/models/event.py

addons/google_calendar/google_calendar.py

addons/hr_holidays/hr_holidays.py

addons/hr_holidays/report/holidays_summary_report.py

addons/hr_payroll/hr_payroll.py

addons/l10n_ch/i18n_extra/de.po

addons/l10n_multilang/account.py

addons/l10n_multilang/l10n_multilang.py

addons/l10n_no/account_tax.xml

addons/mail/models/mail_followers.py

addons/mail/tests/test_mail_followers.py

addons/mass_mailing/static/src/js/mass_mailing_editor.js

addons/payment_paypal/controllers/main.py

addons/payment_paypal/views/payment_acquirer.xml