add identification of Global Caches to WNM (#190) (#191)

* update OGC API - Records - Part 1: Core link to approved document (#188)

* add identification of Global Caches to WNM (#190)

Author: tomkralidis

guide/sections/part2/global-services.adoc

@@ -130,6 +130,7 @@ In WIS2, Global Caches provide access to WMO core data for data consumers. This
 * For messages received on the topic ``++origin/a/+/data/core/#++`` or ``++cache/a/+/data/core/#++``, a Global Cache shall:
 ** If the message contains the property ``"properties.cache": false``,
 *** Republish the message at topic ``cache/a/wis2/...``, matching ``+/a/wis2/...`` where the original message has been received, after having updated the id of the message.
+*** Add the property ``properties.global-cache`` with the value of the centre identifier of the Global Cache to identify the origin of the data source downloaded by downstream applications.
 ** Else
 *** Maintain a list of ``data_id`` values that have already been downloaded;
 *** Verify whether the message points to new or updated data by comparing the pubtime value of the notification message with the list of ``data_id`` values;