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• Have you read the contributing guidelines?
• Have you added tests for any changed functionality?
• Have you added the Jira issue number
  as the first thing in your pull request title (e.g. AO3-1234 Fix thing)
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Issue

https://otwarchive.atlassian.net/browse/AO3-6847

Purpose

Add mailer preview for the anonymous_or_unrevealed_notification email.

Include cucumber test for sending a translated anonymous_or_unrevealed_notification email to a user.

Remove the redundant html_safe call in the HTML mail.

Testing Instructions

See Jira.

References

Credit

Amy Lee