Topics deprecation

Topics is being deprecated and will be removed 2018-9-1

Topic admins/owners will be able to export all of their topics/replies during the deprecation period.

Release checklist

• Merge and release topics export, https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1199
  • Part of 19.10.0, https://gitlab.com/gitlab-org/gitter/webapp/blob/develop/CHANGELOG.md#19100-2018-7-16
• Release blog post
  • Draft (GitLab internal), https://docs.google.com/document/d/17S3CzrZNbIwjWrt2c5eiOl6H0CQ0_mwJBarYLGVYRG0/edit?usp=sharing
  • https://blog.gitter.im/2018/07/16/gitter-topics-deprecation-notice/
• Email topics/forum admins/owners
  • Email list generated from scripts/utils/list-admins-of-every-forum.js from https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1199 and transformed to CSV with quick script
  • Email is sent via GitLab MailChimp account, https://us3.admin.mailchimp.com/campaigns/edit?id=1336629