[Enhancement] Unify the many keyword naming schemes

[Scripter17]

(Split off from #1645 because having 2 things in one issue is dumb)

Different sites have wildly different naming conventions for the keywords in --list-keywords. This is only made worse by some keywords being ambiguous (such as author and user only being different in retweets and stuff)

Issues I've found so far:

• Twitter's author[name] = Reddit's author = Deviantart's author[username]
• Deviantart has published_time for the unix timestamp of a post while twitter just... doesn't

This will completely shatter backwards-compatibility with existing databases, but it's something that needs to get addressed eventually and a hypothetical 2.X seems like a good opportunity

[thatfuckingbird]

A further difficulty with this is that in several cases, parts of the JSON returned from site APIs get added verbatim to the saved metadata. Otherwise some extractors would need a lot more code just to rename/restructure these (sometimes complex) JSON fragments. For this reason, completely unifying the keyword conventions would be much harder than just renaming keys already found in the code.

[mikf]

Deviantart has published_time for the unix timestamp of a post while twitter just... doesn't

Most sites that include some kind of date-time information provide them as date, which is a datetime object that can be formatted with strftime format codes ({date:%Y-%m-%d})

Timestamps can be converted to datetime with d and then formatted like above ({published_time!d:%Y-%m-%d}) and datetime objects can be converted to timestamp with T ({date!T})

[github-account1111]

Timestamps can be converted to datetime

Would it be possible to format something like 8-3-2021 (what Behance use I think)? They don't seem to allow non-zero-padded months and days.

[rautamiekka]

8-3-2021

A pure maintenance and sorting nightmare right there.