Break util.cr into multiple files

src/handlers/auth_handler.cr

@@ -1,6 +1,6 @@
 require "kemal"
 require "../storage"
-require "../util"
+require "../util/*"
 
 class AuthHandler < Kemal::Handler
   # Some of the code is copied form kemalcr/kemal-basic-auth on GitHub

src/handlers/static_handler.cr

@@ -1,6 +1,6 @@
 require "baked_file_system"
 require "kemal"
-require "../util"
+require "../util/*"
 
 class FS
   extend BakedFileSystem

src/handlers/upload_handler.cr

@@ -1,5 +1,5 @@
 require "kemal"
-require "../util"
+require "../util/*"
 
 class UploadHandler < Kemal::Handler
   def initialize(@upload_dir : String)