add new variable for extra configuratuon in elasticsearch.yml (#299)

Close #298

---------

Co-authored-by: Thomas Widhalm <thomas.widhalm@netways.de>
Co-authored-by: Tobias Bauriedel <tobias@bauriedel.de>

Author: 3 people

docs/role-elasticsearch.md

@@ -32,6 +32,19 @@ Role Variables
 * *elasticsearch_check_calculation*: End play in checks (Default: `false`)
 * *elasticsearch_network_host*: You can configure multipe network addresses where the networking is bind to. You can assign IP addresses or interfaces by their names. You can also use elasticsearch internal variabels as it set as default. Example: `"_ens190_,_local_"` (Default: `"_local_,"_site_"`) (Optional; if not defined `default` is used)
 
+* *elasticsearch_extra_config*: You can set additional configuration in YAML-notation as you would write in the `elasaticsearch.yml`. Example:
+
+```YAML
+...
+elasticsearch_extra_config:
+  xpack.security.authc.token.enabled: true
+
+    xpack.security.authc.realms:
+        native.native1:
+            order: 0
+            enabled: true
+```
+
 This variable activates a workaround to start on systems that have certain hardening measures active. See [Stackoverflow](https://stackoverflow.com/questions/47824643/unable-to-load-jna-native-support-library-elasticsearch-6-x/50371992#50371992) for details and logmessages to look for. **WARNING**: This will change your `/etc/sysconfig/elasticseach`or `/etc/default/elasticsearch` file and overwrite `ES_JAVA_OPTS`. See this [issue](https://github.com/netways/ansible-role-elasticsearch/issues/79) for details.
 
 * *elasticsearch_jna_workaround*: Activate JNA workaround. (default: `false`)

roles/elasticsearch/templates/elasticsearch.yml.j2

@@ -75,3 +75,7 @@ path:
 
 {% endfor %}
 {% endif %}
+
+{% if elasticsearch_extra_config is defined %}
+{{ elasticsearch_extra_config | to_nice_yaml(indent=2, sort_keys=False) }}
+{% endif %}