Move list of payment methods to where it is used

app/controllers/spree/admin/payment_methods_controller.rb

@@ -117,7 +117,7 @@ module Spree
       end
 
       def validate_payment_method_provider
-        valid_payment_methods = Rails.application.config.spree.payment_methods.map(&:to_s)
+        valid_payment_methods = Spree::PaymentMethod.providers.map(&:to_s)
         return if valid_payment_methods.include?(params[:payment_method][:type])
 
         flash[:error] = Spree.t(:invalid_payment_provider)

app/models/spree/payment_method.rb

@@ -53,7 +53,11 @@ module Spree
     }
 
     def self.providers
-      Rails.application.config.spree.payment_methods
+      [
+        Spree::PaymentMethod::Check,
+        Spree::Gateway::StripeSCA,
+        Spree::Gateway::PayPalExpress,
+      ]
     end
 
     def configured?

config/application.rb

@@ -76,16 +76,6 @@ module Openfoodnetwork
       end
     end
 
-    initializer "spree.register.payment_methods" do |app|
-      Rails.application.reloader.to_prepare do
-        app.config.spree.payment_methods = [
-          Spree::PaymentMethod::Check,
-          Spree::Gateway::StripeSCA,
-          Spree::Gateway::PayPalExpress,
-        ]
-      end
-    end
-
     initializer "spree.mail.settings" do |_app|
       Rails.application.reloader.to_prepare do
         Spree::Core::MailSettings.init