AO3-7568 Fix Error 500 when importing a work with a numeric date

[hab-bang]

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Issue

https://otwarchive.atlassian.net/browse/AO3-7568

Purpose

Fixing the misspelled constant in StoryParser#convert_revised_at that returns an Error 500 when a work's date is a plain number.

The method treats an all-digit date as seconds since the epoch. That branch calls Regex.last_match, but the class is Regexp, so it raises uninitialized constant StoryParser::Regex. The method only rescues ArgumentError and TypeError, so the error escapes the import and the user gets a 500.

Testing Instructions

Follow the reproduction steps on the Jira issue (Post > Import Work with the gist URL from the ticket, and any language):

• Before this change: Error 500 (NameError: uninitialized constant StoryParser::Regex).
• After this change: the work imports and you get the work preview.

The date shows as 1970-01-04, because the parser reads an all-numeric date as a Unix timestamp. That is existing behaviour and is not changed here, so it is expected.

Full testing instructions are also on the Jira ticket.

References

Reported from Sentry, issue AO3-STAGING-8Y.

Credit

Name: hayoung
Pronouns: she/her