Character encoding for the application/x-www-form-urlencoded format

[adeinega]

Section 3.2.2 Tokens states that

The client makes a request to the token endpoint by sending the
following parameters using the application/x-www-form-urlencoded
format per Appendix B with a character encoding of UTF-8 in the HTTP
request content:

However, the following example does not include UTF-8 as character encoding

POST /token HTTP/1.1
Host: server.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded

it should look like as

POST /token HTTP/1.1
Host: server.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded; charset=UTF-8;

the same applies for all other similar examples in the spec.

How is this important? In some (rare) cases, it can lead to interoperability issues as app servers & frameworks that run an AS do not necessarily use "UTF-8" as a default encoding character, as an example, Java Servlets use "ISO-8859-1". So, it is better for a client to always specify the character explicitly.

[aaronpk]

From what I can tell, the application/x-www-form-urlencoded content type implies UTF-8 encoding, so it is not needed to include the charset.

https://url.spec.whatwg.org/#application/x-www-form-urlencoded

https://url.spec.whatwg.org/#application/x-www-form-urlencoded