roles/mongodb: Add MongoDB deployment

The *mongodb* role installs MongoDB from the *mongodb.org* Yum
repository and manages basic server configuration.

roles/mongodb/defaults/main.yml

@@ -0,0 +1 @@
+mongodb_version: '4.0'

roles/mongodb/tasks/main.yml

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+- name: ensure mongodb package repository is available
+  template:
+    src=mongodb.repo.j2
+    dest=/etc/yum.repos.d/mongodb.repo
+    mode=0644
+  tags:
+  - install
+- name: ensure mongodb is installed
+  package:
+    name: mongodb-org-server
+    state: present
+  tags:
+  - install
+
+- name: ensure mongodb server starts at boot
+  service:
+    name=mongod
+    enabled=yes

roles/mongodb/templates/mongodb.repo.j2

@@ -0,0 +1,6 @@
+[mongodb-org-{{ mongodb_version }}]
+name=MongoDB Repository
+baseurl=https://repo.mongodb.org/yum/redhat/7/mongodb-org/{{ mongodb_version }}/x86_64/
+gpgcheck=1
+enabled=1
+gpgkey=https://www.mongodb.org/static/pgp/server-{{ mongodb_version }}.asc