feat: new user-domain-changed event format

Add the `domains` attribute to event's payload. The value is a list of
domains. The old `domain` attribute is still present and will equal to
a random list element.

This new event format with multiple domains is necessary to reduce the
size of the event burst generated by Ldapproxy when a node joins the
cluster.

Author: DavidePrincipi

core/imageroot/var/lib/nethserver/cluster/actions/alter-external-domain/50alter_ldap_domain

@@ -44,5 +44,6 @@ if protocol == 'ldap':
     }))
     # Advertise new user domain setup
     rdb.publish(os.getenv('AGENT_ID') + '/event/user-domain-changed', json.dumps({
-        'domain': domain
+        'domain': domain, # obsolete
+        'domains': [domain], # since core 3.16.0
     }))

docs/core/events.md

@@ -22,7 +22,8 @@ Events should respect the following rules:
 Well known events:
 - `user-domain-changed`: the user domain has become available, has been
   removed, or its configuration has changed. The JSON parameter format is
-  `{"node_id":INT,"domain":STRING}`. The `node_id` attribute is optional.
+  `{"node_id":INT,"domains":LIST[STRING]}`. The `node_id` attribute is not
+  present for external domains. `domains` is a list of domain names.
 - `ldap-provider-changed`: an external LDAP account provider was removed
   or added to a user-domain. The JSON parameter format is
   `{"domain":STRING,"key":STRING}`.

docs/core/user_domains.md

@@ -61,8 +61,10 @@ event handler. Create an executable script with path
 `${AGENT_INSTALL_DIR}/events/user-domain-changed/10handler`. For instance:
 
 ```shell
-read -r domain < <(jq -r .domain)
-if [[ "${domain}" == "mydomain" ]]; then
+mydomain="ad.example.org"
+
+# Check if $mydomain is in the list of changed domains
+if jq -e --arg d "$mydomain" '.domains | index($d)' >/dev/null; then
     systemctl --user reload mymodule.service
 fi
 ```