Now onto chapter 2.
This is where having a moving library makes books like this difficult to keep upto date.
phx_gen_auth is now part of phoenix as of 1.6.
However it is a bit harder to work that out from the docs.
Adding the dependency leads to a mix resolution conflict.
:phx_gen_auth is listed as 0.4 in the book, The latest version available is 0.7.0
However that only works with phoenix 1.5.2, where as the latest version is 1.6.15
phx_gen_auth has now vanished from hex.pm, and the github project is archived.
Here is the project currently at the end of chapter 2