Add ability to add custom configuration for RabbitMQ

This implements a new variable  rabbitmq_custom_config  to
be able to place custom configuration to the rabbitmq.conf
e.g. to configure installed plugins

Change-Id: I952eefe646b00f60184f8d353f6f055bbdc4ac90

defaults/main.yml

@@ -292,6 +292,8 @@ rabbitmq_port_bindings:
   tcp_listeners:
     "0.0.0.0": 5672
 
+rabbitmq_additional_config: {}
+
 rabbitmq_init_overrides:
   Service:
     LimitNOFILE: "{{ rabbitmq_ulimit }}"

doc/source/configure-rabbitmq.rst

@@ -34,3 +34,17 @@ between each OpenStack service and RabbitMQ.
 Setting this variable to ``false`` disables SSL encryption between
 OpenStack services and RabbitMQ and configures all services to
 use the plain text port, 5672.
+
+Add custom configuration to RabbitMQ
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To add custom configuration, e.g. to configure installed plugins,
+can be accomplished by defining a variable ``rabbitmq_additional_config``
+and add you configuration as a block to this variable. Make sure to
+not add redundent configuration
+
+.. code-block:: yaml
+
+   rabbitmq_additional_config:
+      prometheus.tcp.port: 15680
+      prometheus.tcp.ip: 0.0.0.0

releasenotes/notes/rabbitmq_additional_config-8d5c0c0b6fc6d750.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Add ``rabbitmq_additional_config`` to be able to add additional
+    configuration e.g. to add configuration for plugins.

templates/rabbitmq.conf.j2

@@ -74,3 +74,11 @@ management.ssl.fail_if_no_peer_cert = {{ rabbitmq_ssl_fail_if_no_peer_cert | low
 management.tcp.ip = {{ rabbitmq_management_bind_address }}
 management.tcp.port = {{ rabbitmq_management_bind_tcp_port }}
 {% endif %}
+
+{% if rabbitmq_additional_config | length > 0 %}
+# Custom configuration
+
+{% for config_key, config_value in rabbitmq_additional_config.items() %}
+{{ config_key }} = {{ config_value }}
+{% endfor %}
+{% endif %}