mandrill 8.x-1.0

Changes since 8.x-1.0-alpha1:

• #2765233 by kpoornima: Removed deprecated method l from code base
• #2812637 by iwant2fly: 500 Error on status report if library is not installed
• #2814103 by oadaeh: Change how mail keys are selected for Email key select list on Add Mandrill Template Map page
• #2775171 by joco_sp, oadaeh: Problem when creating new Article
• #2766101 by Andreas Radloff, spoit: Use get for config, not getEditable because it does not load from settings.local.php
• #2802957 by GloGi: Mail sending fails when no subaccounts selected
• #2792899 by swentel: Inject MailManagerInterface instead of MailsystemManager in admin settings form
• #2773419 by Rohit Patil: Remove @file doc block from namespaced classes, interfaces and traits
• #2728493 by lhangea: Remove dependency on composer_manager module
• Ensure we always have a from email and name by defaulting to the site default email and name if either is not set in the mandrill admin settings.
• Use site email address if no "from" address is set in the mandrill admin config.
• Allow "email key" to be specified on the MandrillTemplateMapForm when the mailsystem config is mandrill_test_mail in addition to mandrill_mail.
• Fix bug where email subjects of type string caused fatal error when MandrillTestMail plugin is set as mailsystem sender.
• Ensure mandrill_mail or mandrill_test_mail plugins are being used before exposing the "Send Test Email" form at /admin/config/services/mandrill/test.
• Use selected Mandrill mailer plugin when sending admin test email via MandrillAdminTestForm.