The Author table has a Link field which is available via the Manage Authors feature. If you put a URL in it then, when you click on an Author name in Book details, the URL will open.
It can be any url that has a designated default protocol handler installed. I've used http, file, evernote, onenote, and mailto URLs.
Also see
The calibre:// URL scheme. I use this feature to link Author names in my "Books" library to a record in a separate "Authors" library where I have Author specific custom columns. Entries in "Authors" library link to their records in the Books library. I also use it to link related books.
BR