feat(elasticsearch): add role for single-node deployment using docker containers

roles/elasticsearch/README.md

@@ -0,0 +1,22 @@
+# `finallycoffee.services.elastiscsearch`
+
+A simple ansible role which deploys a single-node elastic container to provide
+an easy way to do some indexing.
+
+## Usage
+
+Per default, `/opt/elasticsearch/data` is used to persist data, it is
+customizable by using either `elasticsearch_base_path` or `elasticsearch_data_path`.
+
+As elasticsearch be can be quite memory heavy, the maximum amount of allowed RAM
+can be configured using `elasticsearch_allocated_ram_mb`, defaulting to 512 (mb).
+
+The cluster name and discovery type can be overridden using
+`elasticsearch_config_cluster_name` (default: elastic) and
+`elasticsearch_config_discovery_type` (default: single-node), should one
+need a multi-node elasticsearch deployment.
+
+Per default, no ports or networks are mapped, and explizit mapping using
+either ports (`elasticsearch_container_ports`) or networks
+(`elasticsearch_container_networks`) is required in order for other services
+to use elastic.