6. Add webhook endpoints to user developer settings screen

Allowing creation and deleting via the user association.
It probably won't be much effort to allow editing and multiple records, but I cut it down to the minimum needed to avoid any further delays.

I couldn't find a way to test a failure in the destroy method, but decided to keep the condition because I thought it was worth having.

app/controllers/webhook_endpoints_controller.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+class WebhookEndpointsController < ::BaseController
+  before_action :load_resource, only: :destroy
+
+  def create
+    webhook_endpoint = spree_current_user.webhook_endpoints.new(webhook_endpoint_params)
+
+    if webhook_endpoint.save
+      flash[:success] = t('.success')
+    else
+      flash[:error] = t('.error')
+    end
+
+    redirect_to redirect_path
+  end
+
+  def destroy
+    if @webhook_endpoint.destroy
+      flash[:success] = t('.success')
+    else
+      flash[:error] = t('.error')
+    end
+
+    redirect_to redirect_path
+  end
+
+  def load_resource
+    @webhook_endpoint = spree_current_user.webhook_endpoints.find(params[:id])
+  end
+
+  def webhook_endpoint_params
+    params.require(:webhook_endpoint).permit(:url)
+  end
+
+  def redirect_path
+    if request.referer.blank? || request.referer.include?(spree.account_path)
+      developer_settings_path
+    else
+      request.referer
+    end
+  end
+
+  def developer_settings_path
+    "#{spree.account_path}#/developer_settings"
+  end
+end