Fixes #36729 - Implement pruning outdated TFTP files

This is about replacing foreman_maintain's check_tftp_storage[1] with a
native implementation. It is implemented by a /tftp/prune API endpoint
which accepts the duration as a parameter.

There is no plugin capability defined since Foreman can just call the
endpoint and process HTTP 404 as Not Implemented.

[1]: https://github.com/theforeman/foreman_maintain/blob/1e20bbd9f32a4f47193c4833fbd4012772b34dc4/definitions/checks/foreman_proxy/check_tftp_storage.rb

modules/tftp/server.rb

@@ -63,6 +63,12 @@ def delete_file(file)
         logger.debug "TFTP: Skipping a request to delete a file which doesn't exists"
       end
     end
+
+    def self.outdated_files(duration)
+      Dir.glob(File.join(Proxy::TFTP::Plugin.settings.tftproot, "boot", "*-{vmlinuz,initrd.img}")).filter do |file|
+        File.file?(file) && (File.mtime(file) + (token_duration * 60)) < Time.now
+      end
+    end
   end
 
   class Syslinux < Server

modules/tftp/tftp_api.rb

@@ -71,5 +71,19 @@ def create_default(variant)
     get "/serverName" do
       {"serverName" => (Proxy::TFTP::Plugin.settings.tftp_servername || "")}.to_json
     end
+
+    # Purge old entries
+    post "/prune" do
+      duration = params[:duration]
+
+      if duration.nil? || duration.to_i <= 0
+        log_halt 400, "Invalid duration; needs to be a valid integer > 0"
+      end
+
+      Proxy::TFTP::Server.outdated_files(duration.to_i).each do |file|
+        logger.debug("Removing outdated file", file)
+        File.unlink(file)
+      end
+    end
   end
 end