Limit importers and exporters by user

Refs
- #123

Prior work limited the ability to view the importer and exporter pages
by user role, but did not limit what importers and exporters could be
seen.

With this work, only admin users can see all importers and exporters,
while other users can only see importers and exporters they have created.

app/controllers/bulkrax/exporters_controller_decorator.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# Override Bulkrax main (at v5.3.0) to limit access to only user's own exporters
+module Bulkrax
+  module ExportersControllerDecorator
+    def index
+      # NOTE: We're paginating this in the browser.
+      @exporters = Exporter.order(created_at: :desc)
+      @exporters = @exporters.where(user: current_user) unless current_ability.admin?
+      @exporters = @exporters.all
+
+      add_exporter_breadcrumbs if defined?(::Hyrax)
+    end
+
+    private
+
+      def check_permissions
+        if current_ability.can_import_works?
+          return true if current_ability.admin?
+          return true unless params.key?(:id)
+          return true if Importer.where(id: params[:id], user: current_user).exists?
+          raise CanCan::AccessDenied
+        else 
+          raise CanCan::AccessDenied
+        end
+      end
+  end
+end
+
+Bulkrax::ExportersController.prepend(Bulkrax::ExportersControllerDecorator)

app/controllers/bulkrax/importers_controller_decorator.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+# Override Bulkrax main (at v5.3.0) to limit access to only user's own importers
+module Bulkrax
+  module ImportersControllerDecorator
+    # GET /importers
+    def index
+      # NOTE: We're paginating this in the browser.
+      @importers = Importer.order(created_at: :desc)
+      @importers = @importers.where(user: current_user) unless current_ability.admin?
+      @importers = @importers.all
+
+      if api_request?
+        json_response('index')
+      elsif defined?(::Hyrax)
+        add_importer_breadcrumbs
+      end
+    end
+
+    private
+
+      def check_permissions
+        if current_ability.can_import_works?
+          return true if current_ability.admin?
+          return true unless params.key?(:id)
+          return true if Importer.where(id: params[:id], user: current_user).exists?
+          raise CanCan::AccessDenied
+        else 
+          raise CanCan::AccessDenied
+        end
+      end
+  end
+end
+
+Bulkrax::ImportersController.prepend(Bulkrax::ImportersControllerDecorator)