refactor: remove facade

Refactored RSS feed handling in app.rb to eliminate the Html2rssFacade.
Merged configuration directly into request handlers, simplifying the feed generation process.
This change enhances performance by reducing method calls and improves readability by consolidating logic.
Removed unused helper files related to the facade, cleaning up the codebase.

Signed-off-by: Gil Desmarais <git@desmarais.de>

Author: gildesmarais

app.rb

@@ -98,7 +98,7 @@ def self.development? = ENV['RACK_ENV'] == 'development'
 
           HttpCache.expires(response, feed.channel.ttl.to_i * 60, cache_control: 'public')
 
-          feed.to_xml
+          feed.to_s
         end
 
         r.on String do |config_name_with_ext|
@@ -115,7 +115,7 @@ def self.development? = ENV['RACK_ENV'] == 'development'
 
           HttpCache.expires(response, feed.channel.ttl.to_i * 60, cache_control: 'public')
 
-          feed.to_xml
+          feed.to_s
         end
       end