Instance helper to replace site title helper (#2038)

* Move site title helper to instance helper (name change only)

* Remove newline in <title> tag

* Add site_hostname helper method to wrap up local_domain value

* Use site_hostname helper in places that need local_domain value

spec/helpers/instance_helper_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe InstanceHelper do
+  describe 'site_title' do
+    it 'Uses the Setting.site_title value when it exists' do
+      Setting.site_title = 'New site title'
+
+      expect(helper.site_title).to eq 'New site title'
+    end
+
+    it 'returns empty string when Setting.site_title is nil' do
+      Setting.site_title = nil
+
+      expect(helper.site_title).to eq ''
+    end
+  end
+
+  describe 'site_hostname' do
+    around(:each) do |example|
+      before = Rails.configuration.x.local_domain
+      example.run
+      Rails.configuration.x.local_domain = before
+    end
+
+    it 'returns the local domain value' do
+      Rails.configuration.x.local_domain = 'example.com'
+
+      expect(helper.site_hostname).to eq 'example.com'
+    end
+  end
+end

spec/helpers/site_title_helper_spec.rb

@@ -1,15 +0,0 @@
-require "rails_helper"
-
-describe "site_title" do
-  it "Uses the Setting.site_title value when it exists" do
-    Setting.site_title = "New site title"
-
-    expect(helper.site_title).to eq "New site title"
-  end
-
-  it "returns empty string when Setting.site_title is nil" do
-    Setting.site_title = nil
-
-    expect(helper.site_title).to eq ""
-  end
-end