Fix the standard generator alias

This generator is here for anyone trying to run th standard
`bin/rails g solidus_auth_devise:install`. Turns out that assigning
to another constant is not enough and we need to proxy it more
explicitly.

Author: elia

lib/generators/solidus_auth_devise/install/install_generator.rb

@@ -1,8 +1,18 @@
 # frozen_string_literal: true
 
 require_relative '../../solidus/auth/install/install_generator'
+
 module SolidusAuthDevise
   module Generators
-    InstallGenerator = ::Solidus::Auth::Generators::InstallGenerator
+    class InstallGenerator < Rails::Generators::Base
+      # Copy over any class option from the legacy install generator
+      Solidus::Auth::Generators::InstallGenerator.class_options.each do |name, option|
+        class_options[name] ||= option.dup
+      end
+
+      def forward_to_spree_auth_install
+        generate 'solidus:auth:install', *ARGV
+      end
+    end
   end
 end

lib/solidus_auth_devise/engine.rb

@@ -1,7 +1,3 @@
 # frozen_string_literal: true
 
 require 'spree/auth/engine'
-
-module SolidusAuthDevise
-  Engine = ::Spree::Auth::Engine
-end

lib/spree/auth/engine.rb

@@ -95,3 +95,5 @@ def self.prepare_frontend
     end
   end
 end
+
+SolidusAuthDevise::Engine = Spree::Auth::Engine