allow author override in front matter

_includes/author-profile.html

 <!-- {% assign author = page.author | default: page.authors[0] | default: site.author %} -->
+{% unless page.author %}
   {% assign author = page.url | split: "/" %}
   {% assign author = author[1] %}
-{% assign author = site.data.authors.authors | where: "prefix", author | first %}
+{% endunless %}
+{% assign author = site.data.authors.authors | where: "directory", author | first %}
 
 <div itemscope itemtype="https://schema.org/Person">
 

_includes/seo.html

@@ -25,6 +25,7 @@
   {%- assign seo_description = seo_description | markdownify | strip_html | strip_newlines | escape_once -%}
 {%- endif -%}
 
+<!-- don't use page.author even if it is set, find author based on url -->
 {% assign author = page.url | split: "/" %}
 {% assign author = author[1] %}
 {% assign author = site.data.authors.authors | where: "prefix", author | first %}

_layouts/single.html

@@ -2,9 +2,11 @@
 layout: default
 ---
 
+{% unless page.author %}
   {% assign author = page.url | split: "/" %}
   {% assign author = author[1] %}
-{% assign author = site.data.authors.authors | where: "prefix", author | first %}
+{% endunless %}
+{% assign author = site.data.authors.authors | where: "directory", author | first %}
 
 {% if page.has_header %}
   {% include page__hero.html %}