Move subdomain logic to tenant model

We had some of the logic in the ApplicationMailer. Since we're going to
use this logic in more places, we're moving it to the Tenant model,
which is the model handling everything related to hosts.

app/mailers/application_mailer.rb

@@ -7,24 +7,10 @@ class ApplicationMailer < ActionMailer::Base
   before_action :set_asset_host
 
   def default_url_options
-    if Tenant.default?
-      super
-    else
-      super.merge(host: host_with_subdomain_for(super[:host]))
-    end
+    Tenant.current_url_options
   end
 
   def set_asset_host
     self.asset_host ||= root_url.delete_suffix("/")
   end
-
-  private
-
-    def host_with_subdomain_for(host)
-      if host == "localhost"
-        "#{Tenant.current_schema}.lvh.me"
-      else
-        "#{Tenant.current_schema}.#{host}"
-      end
-    end
 end

app/models/tenant.rb

@@ -27,22 +27,36 @@ class Tenant < ApplicationRecord
     %w[mail public shared_extensions www]
   end
 
-  def self.default_host
-    ActionMailer::Base.default_url_options[:host]
+  def self.default_url_options
+    ActionMailer::Base.default_url_options
   end
 
-  def self.current_schema
-    Apartment::Tenant.current
+  def self.default_host
+    default_url_options[:host]
   end
 
   def self.current_url_options
-    ApplicationMailer.new.default_url_options
+    default_url_options.merge(host: current_host)
+  end
+
+  def self.current_host
+    if default?
+      default_host
+    elsif default_host == "localhost"
+      "#{current_schema}.lvh.me"
+    else
+      "#{current_schema}.#{default_host}"
+    end
   end
 
   def self.default?
     current_schema == "public"
   end
 
+  def self.current_schema
+    Apartment::Tenant.current
+  end
+
   def self.switch(...)
     Apartment::Tenant.switch(...)
   end

spec/lib/tasks/sitemap_spec.rb

@@ -74,7 +74,7 @@ describe "rake sitemap:create", type: :system do
   end
 
   it "generates a sitemap for every tenant" do
-    allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "consul.dev" })
+    allow(Tenant).to receive(:default_url_options).and_return({ host: "consul.dev" })
     FileUtils.rm_f(Dir.glob(Rails.root.join("public", "tenants", "*", "sitemap.xml")))
 
     create(:tenant, schema: "debates")

spec/models/tenant_spec.rb

@@ -3,7 +3,7 @@ require "rails_helper"
 describe Tenant do
   describe ".resolve_host" do
     before do
-      allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "consul.dev" })
+      allow(Tenant).to receive(:default_url_options).and_return({ host: "consul.dev" })
     end
 
     it "returns nil for empty hosts" do
@@ -85,7 +85,7 @@ describe Tenant do
 
     context "default host contains subdomains" do
       before do
-        allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "demo.consul.dev" })
+        allow(Tenant).to receive(:default_url_options).and_return({ host: "demo.consul.dev" })
       end
 
       it "ignores subdomains already present in the default host" do
@@ -120,7 +120,7 @@ describe Tenant do
 
     context "default host is similar to development and test domains" do
       before do
-        allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "mylvh.me" })
+        allow(Tenant).to receive(:default_url_options).and_return({ host: "mylvh.me" })
       end
 
       it "returns nil for the default host" do