plugin: add battery plugin

this change adds the battery plugin

manifests/plugin/battery.pp

@@ -0,0 +1,17 @@
+# https://collectd.org/wiki/index.php/Plugin:Uptime
+class collectd::plugin::battery (
+  $ensure   = 'present',
+  $interval = undef,
+  Optional[Boolean] $values_percentage = undef,
+  Optional[Boolean] $report_degraded   = undef,
+  Optional[Boolean] $query_state_fs    = undef,
+) {
+
+  include ::collectd
+
+  collectd::plugin { 'battery':
+    ensure   => $ensure,
+    interval => $interval,
+    content  => template('collectd/plugin/battery.conf.erb'),
+  }
+}

spec/classes/collectd_plugin_battery_spec.rb

@@ -0,0 +1,65 @@
+require 'spec_helper'
+
+describe 'collectd::plugin::battery', type: :class do
+  on_supported_os(baseline_os_hash).each do |os, facts|
+    context "on #{os} " do
+      let :facts do
+        facts
+      end
+
+      options = os_specific_options(facts)
+      context 'default' do
+        it 'defaults' do
+          content = <<EOS
+# Generated by Puppet
+<LoadPlugin battery>
+  Globals false
+</LoadPlugin>
+
+<Plugin "battery">
+</Plugin>
+
+EOS
+
+          is_expected.to contain_file('battery.load').with(
+            content: content,
+            path: "#{options[:plugin_conf_dir]}/10-battery.conf"
+          )
+        end
+      end
+
+      options = os_specific_options(facts)
+      context 'multiple instances' do
+        let :params do
+          {
+            'values_percentage' => true,
+            'report_degraded'   => false,
+            'query_state_fs'    => true
+          }
+        end
+
+        it 'overrides defaults' do
+          content = <<EOS
+# Generated by Puppet
+<LoadPlugin battery>
+  Globals false
+</LoadPlugin>
+
+<Plugin "battery">
+  ValuesPercentage true
+  ReportDegraded false
+  QueryStateFS true
+</Plugin>
+
+EOS
+
+          is_expected.to contain_class('collectd')
+          is_expected.to contain_file('battery.load').with(
+            content: content,
+            path: "#{options[:plugin_conf_dir]}/10-battery.conf"
+          )
+        end
+      end
+    end
+  end
+end

templates/plugin/battery.conf.erb

@@ -0,0 +1,11 @@
+<Plugin "battery">
+<% if defined? @values_percentage -%>
+  ValuesPercentage <%= @values_percentage %>
+<% end -%>
+<% if defined? @report_degraded -%>
+  ReportDegraded <%= @report_degraded %>
+<% end -%>
+<% if defined? @query_state_fs -%>
+  QueryStateFS <%= @query_state_fs %>
+<% end -%>
+</Plugin>