DEV: update base url links to respect subfolder installs (#27740)

This change eliminates a couple of instances where subfolder urls are badly formatted, in most cases we can use Discourse.base_url_no_prefix to prevent adding the subfolder to the base url.

app/helpers/email_helper.rb

@@ -24,7 +24,7 @@ module EmailHelper
 
   def email_topic_link(topic)
     url, title = extract_details(topic)
-    raw "<a href='#{Discourse.base_url}#{url}' style='color: ##{@anchor_color}'>#{title}</a>"
+    raw "<a href='#{Discourse.base_url_no_prefix}#{url}' style='color: ##{@anchor_color}'>#{title}</a>"
   end
 
   def email_html_template

app/views/email/_mailing_list_post.html.erb

@@ -1,5 +1,5 @@
 <li>
-  <a href='<%= Discourse.base_url + topic.relative_url %>' style='color: #<%= @anchor_color %>'><%= raw format_topic_title(topic.title) %></a>
+  <a href='<%= Discourse.base_url_no_prefix + topic.relative_url %>' style='color: #<%= @anchor_color %>'><%= raw format_topic_title(topic.title) %></a>
   <span><%= post_count %></span>
   <%= category_badge(topic.category, inline_style: true, absolute_url: true) %>
 </li>

lib/email/sender.rb

@@ -171,7 +171,9 @@ module Email
 
           if topic
             if SiteSetting.private_email?
-              @message.header["List-Archive"] = "#{Discourse.base_url}#{topic.slugless_url}"
+              @message.header[
+                "List-Archive"
+              ] = "#{Discourse.base_url_no_prefix}#{topic.slugless_url}"
             else
               @message.header["List-Archive"] = topic.url
             end

spec/helpers/email_helper_spec.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+RSpec.describe EmailHelper do
+  describe "#email_topic_link" do
+    it "respects subfolder" do
+      set_subfolder "/forum"
+      topic = Fabricate(:topic)
+      expect(helper.email_topic_link(topic)).to include("#{Discourse.base_url_no_prefix}/forum/t")
+    end
+  end
+end

spec/models/post_spec.rb

@@ -2238,6 +2238,17 @@ RSpec.describe Post do
     end
   end
 
+  describe "full_url" do
+    it "returns the correct post url with subfolder install" do
+      set_subfolder "/forum"
+      post = Fabricate(:post)
+
+      expect(post.full_url).to eq(
+        "#{Discourse.base_url_no_prefix}/forum/t/#{post.topic.slug}/#{post.topic.id}/#{post.post_number}",
+      )
+    end
+  end
+
   describe "public_posts_count_per_day" do
     before do
       freeze_time_safe