Use the post's author from frontmatter, or else use the author from
the site's config. You MUST have one of these set or else you will
get an error during site generation. I think it's better to force
the user to define an author tag rather than only printing it if
it is defined because it is a good practice to help bots understand
content.
Use the post's meta description if it exists, otherwise use the
one from the site's config. Set them using the "description" key
in frontmatter or site config.
Note: this means there is no way to NOT have a description. You
must have *at least* a site-wide description and *optionally* a
description for each page/post's front matter.
Partials are nice, but blocks are a better base construct. Right
now there is basically only layouts/_default/baseof.html that is
doing most of the work.
See: https://gohugo.io/templates/blocks