set max size for systemd journal

My /var/log/journal was 2.9GB. I'm not sure what a good limit is, but it
certainly is less than that...

group_vars/all

@@ -169,3 +169,6 @@ cryptshot:
           interval: 6
         - level: monthly
           interval: 3
+
+journal:
+    max_size: 500M

roles/base/tasks/journal.yml

@@ -0,0 +1,11 @@
+---
+- name: Create journal config directory
+  file: path=/etc/systemd/journald.conf.d state=directory
+  tags:
+    - journal
+
+- name: Push journal max size config
+  template: src=00-journal-size.conf.j2 dest=/etc/systemd/journald.conf.d/00-journal-size.conf.j2
+  when: journal is defined and journal.max_size is defined
+  tags:
+    - journal

roles/base/tasks/main.yml

@@ -13,3 +13,4 @@
 - include: user.yml
 - include: sudo.yml
 - include: packages.yml
+- include: journal.yml

roles/base/templates/00-journal-size.conf.j2

@@ -0,0 +1,3 @@
+# {{ ansible_managed }}
+[Journal]
+SystemMaxUse={{ journald.max_size }}