Add support for confidential_issues_events webhooks
GitLab 8.12 added an option for webhooks to fire on confidential issue events. See commit a103a5d9cc2f496854d75492fe3f759fad0a913f.
Cc: @ben.boeckel
GitLab 8.12 added an option for webhooks to fire on confidential issue events. See commit a103a5d9cc2f496854d75492fe3f759fad0a913f.
Cc: @ben.boeckel