[libsoup/mcatanzaro/#184: 2/3] negotiate: add link to RFC 4559

[Michael Catanzaro <mcatanzaro src gnome org>]

commit a3d9e6e22e9454025442a8dc8b03a902f7b33588
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Wed May 4 16:00:28 2022 -0500

    negotiate: add link to RFC 4559
    
    Understanding that RFC 4559 exists would help anybody reading the API
    docs, and also anybody working on this file.

 libsoup/auth/soup-auth-negotiate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/libsoup/auth/soup-auth-negotiate.c b/libsoup/auth/soup-auth-negotiate.c
index 5f1c4a12..d39bb69e 100644
--- a/libsoup/auth/soup-auth-negotiate.c
+++ b/libsoup/auth/soup-auth-negotiate.c
@@ -78,7 +78,8 @@ typedef struct {
 /**
  * SOUP_TYPE_AUTH_NEGOTIATE:
  *
- * A #GType corresponding to HTTP-based GSS-Negotiate authentication.
+ * A #GType corresponding to HTTP-based GSS-Negotiate authentication, as
+ * defined by [RFC 4559](https://datatracker.ietf.org/doc/html/rfc4559).
  * #SoupSessions do not support this type by default; if you want to
  * enable support for it, call soup_session_add_feature_by_type(),
  * passing %SOUP_TYPE_AUTH_NEGOTIATE.