Fixes #3215 - Migrate existing Office365 Channel and ExternalSync to new Microsoft365 name.

db/migrate/20201028095957_issue_3215_rename_existing_office365.rb

@@ -0,0 +1,14 @@
+class Issue3215RenameExistingOffice365 < ActiveRecord::Migration[5.2]
+  def change
+
+    # return if it's a new setup
+    return if !Setting.exists?(name: 'system_init_done')
+
+    # migrate existing Channels and ExternalCredential to new name
+
+    # rubocop:disable Rails/SkipsModelValidations
+    Channel.where(area: 'Office365::Account').update_all(name: 'Microsoft365::Account')
+    ExternalCredential.where(name: 'office365').update_all(name: 'microsoft365')
+    # rubocop:enable Rails/SkipsModelValidations
+  end
+end