Add username claim from OAuth provider. (closes #287)

Signed-off-by: Jason Volk <jason@zemos.net>

src/api/client/session/sso.rs

@@ -601,6 +601,11 @@ async fn decide_user_id(
 			.as_deref()
 			.map(str::to_lowercase)
 			.filter(|_| allowed("preferred_username")),
+		userinfo
+			.username
+			.as_deref()
+			.map(str::to_lowercase)
+			.filter(|_| allowed("username")),
 		userinfo
 			.nickname
 			.as_deref()

src/service/oauth/user_info.rs

@@ -16,6 +16,9 @@ pub struct UserInfo {
 	/// The login username we first consider when defined.
 	pub preferred_username: Option<String>,
 
+	/// The login username considered.
+	pub username: Option<String>,
+
 	/// The login username considered if none preferred.
 	pub nickname: Option<String>,