Add task to import current permissions

This commit introduces a simple rake task that imports the
Permission Sets to the DB, then iterates over the
defined permissions on AppConfiguration to create the
RolePermissions.

core/lib/tasks/solidus/import_existing_permission_sets.rake

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+namespace :solidus do
+  desc "Import existing permission sets to role permissions table"
+  task import_existing_permission_sets: :environment do
+    Spree::PermissionSets::Base.subclasses.each do |permission|
+      Spree::PermissionSet.find_or_create_by(name: permission.to_s.split('PermissionSets::').last, set: permission.to_s)
+    end
+
+    Spree::AppConfiguration.new.roles.roles.each do |role_name, role_config|
+      role_config.permission_sets.each do |permission_set|
+        role = Spree::Role.find_or_create_by(name: role_name)
+        permission_set = Spree::PermissionSet.find_by_set(permission_set.name)
+
+        next unless permission_set
+
+        Spree::RolePermission.find_or_create_by!(
+          role: role,
+          permission_set: permission_set
+        )
+      end
+    end
+  end
+end