Populate sitemap.xml with lastmod value

[gneissone]

Is your feature request related to a problem? Please describe.
VIVO pages often do not appear toward the top of search engine results, even if they are the most relevant page. Perusing Google's search guidelines, it appears that they do not consider the update frequency parameter that VIVO includes in its sitemap.xml file.

Describe the solution you'd like
Add 'lastmod' parameter, which Google does consider when indexing pages based on a site map. See https://developers.google.com/search/docs/crawling-indexing/sitemaps/build-sitemap.

Describe alternatives you've considered
N/A

Additional context
This will need to be an optional parameter included for pages, since currently the last modified date is only added to records if they are edited via the UI. As a workaround, site owners could optionally set their own modified date when pushing updates via the API or via a manual upload.

[litvinovg]

I am not sure using lastmod value instead of changefreq would help to improve Google indexing. I tried it last year and it didn't help.