Make the nickname claim conditional on the openid scope too

This is only needed for OIDC anyway

handlers/user/info.go

@@ -61,9 +61,10 @@ func UserInfo(ctx *gin.Context) {
 
 			if s == "openid" {
 				userinfoRes["sub"] = *tokenInfo.Sub
-			} else if s == "username" {
+				if value, ok := (*userinfo)["username"]; ok {
 					// Add "nickname" field for OIDC compatibility
-				userinfoRes["nickname"] = userinfoRes[s]
+					userinfoRes["nickname"] = value
+				}
 			}
 		}
 	}