Split collection notification into two separate mailers

Currently, the collection_notification is used to send the “Assignments sent” mail and the “Challenge default by UserA” mail. We would like to split it into two separate mailer methods and update their text.

The mailers should be coded as translatable and have mailer previews. Their subjects should be defined with default_i18n_subject so that they are fully translatable, including a parameter for the collection title.

The “Assignment default” email should not be sent if any of the users no longer exists.

[AO3][Collection Title] Assignments sent

HTML email

The body should be approximately as follows:

Plain-text email

The body should be approximately as follows:

[AO3][Collection Title] Assignment default by User1

HTML email

The body should be approximately as follows:

Plain-text email

The body should be approximately as follows:

For both emails

sent_at should be set.

There should be a footer_note:

HTML email

When sending the mail to the collection.collection_email it should be approximately:

Otherwise it should be approximately:

This footer note is shared with and , so it should go in the mailer_helper for ease of reuse.

Plain-text email

When sending the mail to the collection.collection_email it should be approximately:

Otherwise it should be approximately:

This footer note is shared with and , so it should go in the mailer_helper for ease of reuse.

Testing

1. On your Preferences page, select a locale other than English

2. Create a collection

3. Create a gift exchange challenge

4. Sign up for this challenge with at least two different accounts

5. Close sign-ups and run matching

6. Send out assignments

7. Default on one of the assignments

The mails sent in step 6 and 7 should match the subject, text and footer described above.