Feature: Slack integration (#783)

- Integrations architecture
- Slack integration

lib/integrations/slack/channel_builder.rb

@@ -0,0 +1,33 @@
+class Integrations::Slack::ChannelBuilder
+  attr_reader :params, :channel
+
+  def initialize(params)
+    @params = params
+  end
+
+  def perform
+    create_channel
+    update_reference_id
+  end
+
+  private
+
+  def hook
+    @hook ||= params[:hook]
+  end
+
+  def slack_client
+    Slack.configure do |config|
+      config.token = hook.access_token
+    end
+    Slack::Web::Client.new
+  end
+
+  def create_channel
+    @channel = slack_client.conversations_create(name: params[:channel])
+  end
+
+  def update_reference_id
+    @hook.reference_id = channel['channel']['id']
+  end
+end