Reimplement relative time formatting as a filter, dropping dependency on deprecated moment.js

[oldnomad]

This PR offers a more complete solution than #1441, and replaces it.

This is a re-implementation of relative date/time formatting (getRelativeDate()), which was mentioned in #1433. Original version used NodeJS module moment.js, which is obsolete, deprecated, and slated for removal from Nextcloud base.

This version implements relative formatting as a filter, instead of a controller method. It uses pure JavaScript Intl.RelativeTimeFormat, with fallback to plain date formatting for older browsers. Dependency on moment.js is dropped. The new function is, however, slightly different from the original:

• If the distance between now and the timestamp is more than 90 days (and for older browsers), absolute date/time format is used. I didn't want to use "N months ago" relative format, since it's difficult to calculate correctly; and "N weeks ago" seems to be less readable for long distances.
• The function returns "N weeks ago" for distances greater than 7 days, "N days ago" for distances greater than 1 day, and so on.
• In the fallback (absolute format) branch the function returns time only to minutes. If the timestamp is within half-day from now, only time is printed; if the timestamp is within 7 days from now, weekday is added; otherwise, full date is added.

[SMillerDev]

LGTM

[codecov-commenter]

Codecov Report

Merging #1450 (6f0e531) into master (9087d89) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head 6f0e531 differs from pull request most recent head 3fa791d. Consider uploading reports for the commit 3fa791d to get more accurate results

@@             Coverage Diff              @@
##             master    #1450      +/-   ##
============================================
+ Coverage     91.93%   91.94%   +0.01%     
  Complexity      759      759              
============================================
  Files            64       64              
  Lines          2776     2769       -7     
============================================
- Hits           2552     2546       -6     
+ Misses          224      223       -1     

Impacted Files	Coverage Δ
lib/Service/FeedServiceV2.php	100.00% <0.00%> (ø)
lib/Command/Debug/ItemList.php	100.00% <0.00%> (ø)
lib/Command/Debug/FeedItemList.php	100.00% <0.00%> (ø)
lib/Command/Debug/FolderItemList.php	100.00% <0.00%> (ø)
lib/Fetcher/FeedFetcher.php	89.11% <0.00%> (+0.44%)	⬆️

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[Grotax]

Could you do a rebase? We merged a fix for the tests.

[oldnomad]

Could you do a rebase? We merged a fix for the tests.

Done.

[anoymouserver]

Works as expected.
I stumbled over the missing months though, even 12 weeks (your 90 days threshold) is not a common unit for me, making this more confusing to me than an absolute date. It's probably personal preference, but find absolute dates better to understand than large relative ones.

Regarding the improved performance, I couldn't do any tests on my test instance.

I'm not sure if this will be a longer term solution or if this will change with the new vue based front end.

[Grotax]

Thank you very much @oldnomad :)

And I assume that with the vue rewrite this might be replaced, maybe until then Nextcloud also has a new lib that respects the Nextlcloud localization