AO3-7238 Add work's last updated time to akismet comment spam checks

[omerfaruk-pseud]

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Issue

https://otwarchive.atlassian.net/browse/AO3-7238

Purpose

Adds the timestamp of modification of the parent which the comment was posted on (revision time for works and creation time for admin posts). It is to improve akismet's comment checks for better spam detection accuracy.

Credit

ömer faruk (he/him)

[sarken]

I think tests similar to these tests of various akismet_attributes' values would be fine. Maybe we could use travel_to to make sure the work and chapter have different revised_at dates and the correct one gets used in the akismet_attribute?

[marcus8448]

Thanks for working on this!

[marcus8448]

Thanks again!