Add a new check which allows checking for extra config

We include configuration from multiple sources, and we wanted a way
to ensure that a list of variables (canaries) have been defined
in our various configuration override repos and then -e@'ed in.

playbooks/roles/common/tasks/main.yml

 ---
+- name: Check Configuration Sources
+  fail:
+    msg: "Configuration Sources Checking (COMMON_EXTRA_CONFIGURATION_SOURCES_CHECKING) is enabled, you must define {{ item }}"
+  when: COMMON_EXTRA_CONFIGURATION_SOURCES_CHECKING and ({{ item }} is not defined or {{ item }} != True)
+  with_items: COMMON_EXTRA_CONFIGURATION_SOURCES
+  tags:
+    - "install"
+    - "install:configuration"
+
 # ubuntu
 - stat: 
     path: "/usr/sbin/update-ca-certificates"

playbooks/roles/common_vars/defaults/main.yml

@@ -191,3 +191,15 @@ common_close_all_caches: |
 
 COMMON_TRACKING_LOG_ROTATION:
   - size 1M
+
+# If you include configuration from multiple sources and want to ensure that
+# all sources are included when running playbooks, this provides a way to check that.
+# As an example, if you have a secure configuration repo, you can do
+# COMMON_EXTRA_CONFIGURATION_SOURCES_CHECKING: true
+# COMMON_EXTRA_CONFIGURATION_SOURCES:
+#  - COMMON_USING_SECURE_REPO
+# The common role will then ensure that COMMON_USING_SECURE_REPO is defined and true.
+# This will ensure that you've included a file that sets
+# COMMON_USING_SECURE_REPO: true
+COMMON_EXTRA_CONFIGURATION_SOURCES_CHECKING: false
+COMMON_EXTRA_CONFIGURATION_SOURCES: []