Improve deploy message

What does this MR do?

Improves deploy message to make it more descriptive and useable then what is already offered by deploy command.

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

lib/gitlab/chat_commands/deploy.rb

 module Gitlab
   module ChatCommands
     class Deploy < BaseCommand
+      include Gitlab::Routing.url_helpers
+
       def self.match(text)
         /\Adeploy\s+(?<from>.*)\s+to+\s+(?<to>.*)\z/.match(text)
       end
@@ -25,7 +27,7 @@ module Gitlab
         return unless actions.present?
         if actions.one?
-          actions.first.play(current_user)
+          play!(from, to, actions.first)
         else
           Result.new(:error, 'Too many actions defined')
         end
@@ -33,12 +35,23 @@ module Gitlab
       private
+      def play!(from, to, action)
+        new_action = action.play(current_user)
+
+        Result.new(:success, "Deployment from #{from} to #{to} started. Follow the progress: #{url(new_action)}.")
+      end
+
       def find_actions(from, to)
         environment = project.environments.find_by(name: from)
         return unless environment
         environment.actions_for(to).select(&:starts_environment?)
       end
+
+      def url(subject)
+        polymorphic_url(
+          [ subject.project.namespace.becomes(Namespace), subject.project, subject ])
+      end
     end
   end
 end