FIX: Add bookmark limits (#11725)

Adds a bookmark search per page limit, a total bookmark creation limit, and a rate limit per day for bookmark creation.

spec/models/user_bookmark_list_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe UserBookmarkList do
+  let(:params) { {} }
+  fab!(:user) { Fabricate(:user) }
+  let(:list) { UserBookmarkList.new(user: user, guardian: Guardian.new(user), params: params) }
+
+  before do
+    22.times do
+      Fabricate(:bookmark, user: user)
+    end
+  end
+
+  it "defaults to 20 per page" do
+    expect(list.per_page).to eq(20)
+  end
+
+  context "when the per_page param is too high" do
+    let(:params) { { per_page: 1000 } }
+
+    it "does not allow more than X bookmarks to be requested per page" do
+      expect(list.load.count).to eq(20)
+    end
+  end
+end