Change `ActionDispatch::Response#content_type` returning Content-Type header as it is

Since #35709, `Response#conten_type` returns only MIME type correctly.
It is a documented behavior that this method only returns MIME type, so
this change seems appropriate.
https://github.com/rails/rails/blob/39de7fac0507070e3c5f8b33fbad6fced84d97ed/actionpack/lib/action_dispatch/http/response.rb#L245-L249

But unfortunately, some users expect this method to return all
Content-Type that does not contain charset. This seems to be breaking
changes.

We can change this behavior with the deprecate cycle.
But, in that case, a method needs that include Content-Type with
additional parameters. And that method name is probably the
`content_type` seems to properly.

So I changed the new behavior to more appropriate `media_type` method.
And `Response#content_type` changed (as the method name) to return Content-Type
header as it is.

Fixes #35709.

[Rafael Mendonça França & Yuuji Yaginuma ]

1 files changed, 1 insertions, 1 deletions

diff --git a/guides/source/testing.md b/guides/source/testing.md
index 9540bb2af5..41bc54b924 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -1144,7 +1144,7 @@ test "ajax request" do
   get article_url(article), xhr: true
 
   assert_equal 'hello world', @response.body
-  assert_equal "text/javascript", @response.content_type
+  assert_equal "text/javascript", @response.media_type
 end
 ```