[xwiki-users] Custom authenticator how to

Hello, I need to implement a custom headers authenticator for XWiki Enterprise 5.1 (it will essentially be like the authenticator in https://github.com/xwiki-contrib/sandbox/tree/master/authenticators/xwiki-a…), but I can't figure out how to do this. Can anyone point me in the right direction? The custom authenticator documentation makes it sound trivial, and I'm sure it is, but I don't know how to go about actually implementing XWikiAuthService (or extending XWikiAuthServiceImpl for that matter) since I don't know where these classes are physically located. I'm trying to learn Maven simultaneously and it's pretty overwhelming. I'd rather not have to read an entire Maven guide just to figure out how to extend a class for XWiki. Thanks!