chore(header): Add support for RFC 9512: application/yaml (#3851)

* fix(binding): support application/yaml

RFC 9512 defines application/yaml as the official YAML MIME type.
application/x-yaml is deprecated. In this commit, we ensure it is
recognized correctly in Content-Type.

* fix(render): use application/yaml when rendering YAML

As per RFC 9512, application/x-yaml is now deprecated and applications
should use application/yaml. This commit fix the Content-Type header
when rendering YAML.

render/render_test.go

@@ -280,12 +280,12 @@ b:
 	d: [3, 4]
 	`
 	(YAML{data}).WriteContentType(w)
-	assert.Equal(t, "application/x-yaml; charset=utf-8", w.Header().Get("Content-Type"))
+	assert.Equal(t, "application/yaml; charset=utf-8", w.Header().Get("Content-Type"))
 
 	err := (YAML{data}).Render(w)
 	assert.NoError(t, err)
 	assert.Equal(t, "|4-\n    a : Easy!\n    b:\n    \tc: 2\n    \td: [3, 4]\n    \t\n", w.Body.String())
-	assert.Equal(t, "application/x-yaml; charset=utf-8", w.Header().Get("Content-Type"))
+	assert.Equal(t, "application/yaml; charset=utf-8", w.Header().Get("Content-Type"))
 }
 
 type fail struct{}

render/yaml.go

@@ -15,7 +15,7 @@ type YAML struct {
 	Data any
 }
 
-var yamlContentType = []string{"application/x-yaml; charset=utf-8"}
+var yamlContentType = []string{"application/yaml; charset=utf-8"}
 
 // Render (YAML) marshals the given interface object and writes data with custom ContentType.
 func (r YAML) Render(w http.ResponseWriter) error {