Global role readme

We're getting to the part where we should have a general readme for the
roles that contains documentation about some global variables that might
be consumed across multiple roles by default. Currently this is limited
to the auth related variables.  Additionally the readme has a basic
example undercloud install playbook to indicate how some of the roles
can be used.

Change-Id: I511b6ace42a08e8669d727aa19c5bc4b51c069a5

roles/README.md

@@ -0,0 +1,92 @@
+tripleo-operator-ansible roles
+==============================
+
+These roles wrap tripleo cli functions for use in automation.
+
+Requirements
+------------
+
+None.
+
+Global Variables
+----------------
+
+Accross the roles, there are a few variables that can be defined and would be
+consumed by default.
+
+* `tripleo_os_cloud`: (String) OS_CLOUD name to use when a command requires authentication. By default this will be used to populate any role specific os_cloud variable that may be defined. If this is defined, it will take precedence over `tripleo_rc_file`.
+* `tripleo_rc_file`: (String) File path on the remote system that contains the authentication environment variables that will be used to perform actions that require authentication.
+
+Dependencies
+------------
+
+None.
+
+Example Playbooks
+-----------------
+
+Example undercloud installation
+
+    ---
+    - hosts: undercloud
+      gather_facts: true
+      collections:
+        - tripleo.operator
+      tasks:
+        - name: Create dummy interface
+          command: ip link add prov type dummy
+          become: true
+          when: not 'prov' in ansible_facts.interfaces
+
+        - name: Set hostname
+          hostname:
+            name: 'undercloud.localdomain'
+          become: true
+
+        - name: Configure tripleo repositories
+          import_role:
+            name: tripleo-repos
+
+        - name: Install python2 tripleoclient
+          package:
+            name: python2-tripleoclient
+            state: present
+          become: true
+          when: ansible_distribution_major_version|int <= 7
+
+        - name: Install python3 tripleoclient
+          package:
+            name: python3-tripleoclient
+            state: present
+          become: true
+          when: ansible_distribution_major_version|int >= 8
+
+        # This uses https://opendev.org/openstack/ansible-config_template
+        - name: Generate undercloud.conf
+          become: True
+          config_template:
+            src: /usr/share/python-tripleoclient/undercloud.conf.sample
+            dest: "{{ ansible_env.HOME }}/undercloud.conf"
+            remote_src: true
+            render_template: false
+            config_overrides:
+              'DEFAULT':
+                  undercloud_debug: true
+                  enable_telemetry: false
+                  local_mtu: 1400
+                  local_interface: prov
+                  undercloud_enable_selinux: false
+              'ctlplane-subnet':
+                  masquerade: true
+            config_type: ini
+
+        - name: Install undercloud
+          import_role:
+            name: tripleo-undercloud-install
+          vars:
+            tripleo_undercloud_install_debug: true
+
+License
+-------
+
+Apache-2.0