When setting up the database, if I run mix ecto.setup without ADMIN_EMAIL env set, it will obviously fail.

However, after setting the env variable, if I run mix ecto.setup again, I will run into this error.

** (ArgumentError) construction of binary failed: segment 2 of type 'binary': expected a binary but got: nil

To fix this, we ought to delete the database created and run mix ecto.setup again, as the initial run without the env variable configured will cause this error in subsequent tries.

I suggest adding a piece of documentation to clarify this.