Add details of cookie name and size to CookieOverflow exception

My app was raising a `CookieOverflow` exception but it was difficult to pinpoint the cause, since error trackers and logging system generally filter out cookies.

This Pull Request has been created because I want the exception to provide additional information:
- The name of the cookie that overflowed
- The magnitude of how much it overflowed by

I am assuming that only the cookie value is sensitive, and not its name or size.

Author: andyw8

actionpack/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Add details of cookie name and size to `CookieOverflow` exception.
+
+    *Andy Waite*
+
 *   Don't double log the `controller` or `action` when using `ActiveRecord::QueryLog`
 
     Previously if you set `config.active_record.query_log_tags` to an array that included

actionpack/lib/action_dispatch/middleware/cookies.rb

@@ -632,7 +632,9 @@ def parse(name, signed_message, purpose: nil)
         def commit(name, options)
           options[:value] = @verifier.generate(serialize(options[:value]), **cookie_metadata(name, options))
 
-          raise CookieOverflow if options[:value].bytesize > MAX_COOKIE_SIZE
+          if options[:value].bytesize > MAX_COOKIE_SIZE
+            raise CookieOverflow, "#{name} cookie overflowed with size #{options[:value].bytesize} bytes"
+          end
         end
     end
 
@@ -684,7 +686,9 @@ def parse(name, encrypted_message, purpose: nil)
         def commit(name, options)
           options[:value] = @encryptor.encrypt_and_sign(serialize(options[:value]), **cookie_metadata(name, options))
 
-          raise CookieOverflow if options[:value].bytesize > MAX_COOKIE_SIZE
+          if options[:value].bytesize > MAX_COOKIE_SIZE
+            raise CookieOverflow, "#{name} cookie overflowed with size #{options[:value].bytesize} bytes"
+          end
         end
     end
 

actionpack/test/dispatch/cookies_test.rb

@@ -852,9 +852,10 @@ def test_delete_and_set_cookie
   end
 
   def test_raise_data_overflow
-    assert_raise(ActionDispatch::Cookies::CookieOverflow) do
+    error = assert_raise(ActionDispatch::Cookies::CookieOverflow) do
       get :raise_data_overflow
     end
+    assert_equal "foo cookie overflowed with size 5522 bytes", error.message
   end
 
   def test_tampered_cookies

actionpack/test/dispatch/session/cookie_store_test.rb

@@ -189,9 +189,10 @@ def test_deserializes_unloaded_classes_on_get_value
 
   def test_close_raises_when_data_overflows
     with_test_route_set do
-      assert_raise(ActionDispatch::Cookies::CookieOverflow) {
+      error = assert_raise(ActionDispatch::Cookies::CookieOverflow) {
         get "/raise_data_overflow"
       }
+      assert_equal "_myapp_session cookie overflowed with size 5612 bytes", error.message
     end
   end