Deprecate using Paperclip as Image/Taxon attachment adapter

We are also providing a message with instructions for who wants
to keep using Paperclip.

We are silencing deprecation warnings when setting the deprecated
configuration in the CI. This will allow us to keep testing if our
code still works with the deprecated adapter.

core/lib/spree/app_configuration.rb

@@ -491,6 +491,18 @@ def payment_canceller
     # @return [Module] a module that can be included into Spree::Image to allow attachments
     # Enumerable of images adhering to the present_image_class interface
     class_name_attribute :image_attachment_module, default: "Spree::Image::ActiveStorageAttachment"
+    def image_attachment_module=(value)
+      if value == 'Spree::Image::PaperclipAttachment'
+        Spree::Deprecation.warn <<~MSG
+          Solidus will remove built-in support for Paperclip as image adapter in the next major version.
+          Please, use the provided generator to incorporate the current Paperclip adapter in your application with:
+
+          bin/rails g solidus:paperclip_adapter:install
+        MSG
+      end
+
+      preferences[:image_attachment_module] = value
+    end
 
     # @!attribute [rw] allowed_image_mime_types
     #
@@ -558,6 +570,19 @@ def payment_canceller
     # @return [Module] a module that can be included into Spree::Taxon to allow attachments
     # Enumerable of taxons adhering to the present_taxon_class interface
     class_name_attribute :taxon_attachment_module, default: "Spree::Taxon::ActiveStorageAttachment"
+    def image_attachment_module=(value)
+      if value == 'Spree::Taxon::PaperclipAttachment'
+        Spree::Deprecation.warn <<~MSG
+          Solidus will remove built-in support for Paperclip as taxons' image adapter in the next major version.
+          Please, use the provided generator to incorporate the current Paperclip adapter in your application with:
+
+          bin/rails g solidus:paperclip_adapter:install
+        MSG
+      end
+
+      preferences[:image_attachment_module] = value
+    end
+
 
     # Configures the absolute path that contains the Solidus engine
     # migrations. This will be checked at app boot to confirm that all Solidus

core/lib/spree/testing_support/dummy_app.rb

@@ -135,8 +135,10 @@ class Application < ::Rails::Application
 Spree.load_defaults(Spree.solidus_version)
 Spree.config do |config|
   if (ENV['DISABLE_ACTIVE_STORAGE'] == 'true')
-    config.image_attachment_module = 'Spree::Image::PaperclipAttachment'
-    config.taxon_attachment_module = 'Spree::Taxon::PaperclipAttachment'
+    Spree::Deprecation.silence do
+      config.image_attachment_module = 'Spree::Image::PaperclipAttachment'
+      config.taxon_attachment_module = 'Spree::Taxon::PaperclipAttachment'
+    end
   end
 end