Fix url in emails, add frontendURL helper (#19)

Fixes #16

spec/helpers/frontend_urls_helper_spec.rb

@@ -0,0 +1,17 @@
+require "rails_helper"
+
+describe FrontendUrlsHelper, type: :helper do
+  describe "#frontend_url" do
+    context "without query params" do
+      it "creates path correctly" do
+        expect(helper.frontend_url('dashboard')).to eq "http://test.host/app/dashboard"
+      end
+    end
+
+    context "with query params" do
+      it "creates path correctly" do
+        expect(helper.frontend_url('dashboard', p1: 'p1', p2: 'p2')).to eq "http://test.host/app/dashboard?p1=p1&p2=p2"
+      end
+    end
+  end
+end