Provide a hook for overriding configuration

Change-Id: Id2e3370c359e530219927e8f89c0c80443031bd9

defaults/main.yml

@@ -36,3 +36,10 @@ ara:
     nginx:
       # Where nginx will store the proxy cache
       cache_directory: /var/cache/nginx
+
+# You can use a variable called ara_override to use custom configuration
+# parameters.
+
+# ara_override:
+#   config:
+#     database: "mysql+pymysql://ara:password@localhost/ara"

tasks/main.yml

@@ -19,6 +19,13 @@
     - "{{ ansible_distribution }}.yml"
     - "{{ ansible_os_family }}.yml"
 
+- name: Override default variables
+  set_fact:
+    ara: "{{ ara | combine(ara_override, recursive=true) }}"
+  when:
+    - ara_override is defined
+    - ara_override is mapping
+
 - name: Install required dependencies
   become: true
   package: