Add Google Scholar expected meta tags to publication pages

[thomwiggers]

Prerequisites

• I have searched for duplicate or closed feature requests
• I am mindful of the project scope

Proposal

https://scholar.google.com/intl/en/scholar/inclusion.html#indexing documents that certain tags are used by Google Scholar specifically for inclusion in that search engine.
Example

<meta name="citation_author" content="First Author">
<meta name="citation_author" content="Second Author">
<meta name="citation_author" content="Third Author">
<meta name="citation_journal_title" content="Some Conference Or Journal 2024">
<meta name="citation_publication_date" content="2024">
<meta name="citation_pdf_url" content="publication.pdf">

Motivation and context

#1264 brought this up before, but ended up being implemented through Schema.org. As Scholar seems on life support, I'm not sure if any of the other metadata (such as Schema.org) is used. Additionally, Schema.org metadata doesn't specifically indicate that an article is scholarly. This additional metadata could serve as a valuable additional signal to Google Scholar specifically.

[thomwiggers]

I've put together the following head-end hook:

Put the following in layouts/partials/hooks/head-end/google-scholar.html:

{{ if .IsPage | and (eq .Type "publication") }}
{{/* based on page_metadata_authors.html */}}
{{- $taxonomy := "authors" }}
{{ if .Param $taxonomy }}
  {{ range $index, $value := (.GetTerms $taxonomy) }}
    <meta name="citation_author" content="{{ .LinkTitle }}" />
  {{- end -}}
{{- end }}

<meta name="citation_title" content="{{ .Title }}" />
<meta name="citation_publication_date" content="{{ .Params.Date.Format "2006/01/02" }}" />

{{ $resource := .Page.Resources.GetMatch (printf "%s.pdf" .Page.File.ContentBaseName) }}
{{ with $resource }}
  <meta name="citation_pdf_url" content="{{ .Permalink }}" />
{{ else }}
  {{ if .Params.url_pdf }}
    <meta name="citation_pdf_url" content="{{ .Params.url_pdf | absURL }}" />
  {{ end }}
{{ end }}

{{ if .Params.publication -}}
{{ if in .Params.publication_types "thesis" -}}
<meta name="citation_dissertation_institution" content="{{ .Params.publication }}" />
{{ else if in .Params.publication_types "paper-conference" }}
<meta name="citation_conference_title" content="{{ .Params.publication }}" />
{{ else if in .Params.publication_types "article-journal" }}
<meta name="citation_journal_title" content="{{ .Params.publication }}" />
{{- end }}
{{- end }}
{{- end }}