lib: implement server metrics

lib/hcloud/server.rb

@@ -22,6 +22,7 @@ class Server
  destructible
 
  has_actions
+ has_metrics
 
  def enable_rescue(type: 'linux64', ssh_keys: [])
  query = COLLECT_ARGS.call(__method__, binding)

spec/hcloud/server_spec.rb

@@ -7,6 +7,7 @@
 require 'support/it_supports_update'
 require 'support/it_supports_destroy'
 require 'support/it_supports_labels_on_update'
+require 'support/it_supports_metrics'
 require 'support/it_supports_action_fetch'
 
 RSpec.describe Hcloud::Server, doubles: :server do
@@ -26,6 +27,7 @@
  include_examples 'it_supports_update', described_class, { name: 'new_name' }
  include_examples 'it_supports_destroy', described_class
  include_examples 'it_supports_labels_on_update', described_class
+ include_examples 'it_supports_metrics', described_class, %i[cpu disk network]
  include_examples 'it_supports_action_fetch', described_class
 
  it 'fetch server' do

spec/support/it_supports_metrics.rb

@@ -25,6 +25,10 @@ def build_metrics(params)
  end: params[:end],
  step: step,
  time_series: {
+ # In reality the time series name does not necessarily have to be the same
+ # as the queried type. E.g. server metrics for the type "network" returns multiple time
+ # series called "network.0.pps.in", "network.0.pps.out" and so on. But for our unit
+ # tests returning a single time series is enough at the moment.
  params[:type].to_sym => {
  # generate a random length list of a few random values
  values: Array.new(Faker::Number.within(range: 0..100)).map.with_index do |_, idx|