Set copyright year to publishing year

Falls back to the current year for unpublished articles.

Fixes: #94

Author: tarleb

data/filters/time.lua

@@ -41,5 +41,8 @@ function Meta (meta)
 
   meta.submitted = format_date(meta.submitted_parts)
   meta.published = format_date(meta.published_parts)
+
+  meta.copyright = meta.copyright or {}
+  meta.copyright.year = meta.published_parts.year
   return meta
 end

test/expected-draft/paper.jats/paper.jats

@@ -88,7 +88,7 @@ publishing pipeline</article-title>
 <copyright-statement>Authors of papers retain copyright and release the
 work under a Creative Commons Attribution 4.0 International License (CC
 BY 4.0)</copyright-statement>
-<copyright-year>2022</copyright-year>
+<copyright-year>1970</copyright-year>
 <copyright-holder>The article authors</copyright-holder>
 <license license-type="open-access" xlink:href="https://creativecommons.org/licenses/by/4.0/">
 <license-p>Authors of papers retain copyright and release the work under

test/expected-pub/paper.jats/paper.jats

@@ -88,7 +88,7 @@ publishing pipeline</article-title>
 <copyright-statement>Authors of papers retain copyright and release the
 work under a Creative Commons Attribution 4.0 International License (CC
 BY 4.0)</copyright-statement>
-<copyright-year>2022</copyright-year>
+<copyright-year>2020</copyright-year>
 <copyright-holder>The article authors</copyright-holder>
 <license license-type="open-access" xlink:href="https://creativecommons.org/licenses/by/4.0/">
 <license-p>Authors of papers retain copyright and release the work under