Add abstract definition for debug_message (#1927)

Author: garymardell

src/lucky/data_response.cr

@@ -31,7 +31,8 @@
 class Lucky::DataResponse < Lucky::Response
   DEFAULT_STATUS = 200
 
-  getter context, data, content_type, filename, debug_message, headers
+  getter context, data, content_type, filename, headers
+  getter debug_message : String?
 
   def initialize(@context : HTTP::Server::Context,
                  @data : String,

src/lucky/file_response.cr

@@ -41,7 +41,8 @@
 class Lucky::FileResponse < Lucky::Response
   DEFAULT_STATUS = 200
 
-  getter context, path, filename, debug_message, headers
+  getter context, path, filename, headers
+  getter debug_message : String?
 
   def initialize(@context : HTTP::Server::Context,
                  @path : String,

src/lucky/response.cr

@@ -1,4 +1,5 @@
 abstract class Lucky::Response
   abstract def print
   abstract def status : Int
+  abstract def debug_message : String?
 end

src/lucky/text_response.cr

@@ -10,7 +10,8 @@
 class Lucky::TextResponse < Lucky::Response
   DEFAULT_STATUS = 200
 
-  getter context, content_type, body, debug_message, enable_cookies
+  getter context, content_type, body, enable_cookies
+  getter debug_message : String?
 
   def initialize(@context : HTTP::Server::Context,
                  @content_type : String,