refactor: error handling return exception message

app/lib/errors.cr

@@ -2,8 +2,9 @@ require "kemal"
 
 module App
   class BadRequestException < Kemal::Exceptions::CustomException
-    def initialize(context)
+    def initialize(context, message = Hash(String, String))
       context.response.status_code = 400
+      context.response.print({ "error" => message }.to_json)
       super(context)
     end
   end
@@ -16,11 +17,10 @@ module App
   end
 
   class UnprocessableEntityException < Kemal::Exceptions::CustomException
-    def initialize(context, @content = "")
+    def initialize(context, message = Hash(String, String))
       context.response.status_code = 422
+      context.response.print({ "error" => message }.to_json)
       super(context)
     end
-
-    getter :content
   end
 end