How to create new sftp user with access to /var/www

In what appears to be the new way I do things (i.e. here and here), following a question from TurnKey Hub user Rob, I'm posting this "tutorial" as a blog post.

Install newer (or latest) PostgreSQL on TurnKey

PostgreSQL logo

TurnKey Hub user Vishal recently asked about installing PostgreSQL v14+ on TurnKey. He noted that he was interested in Postgres 14 or higher because of the new IVM extension (incrementally updating materialized views). I started answering his support request, but then thought I might as well post this on the blog as perhaps it provides value for others?!

Firstly, some context and background...