Add Testcontainers User-Agent

Closes #42

Author: guilleiguaran

core/lib/testcontainers.rb

@@ -31,4 +31,9 @@ def logger
       @logger ||= Logger.new($stdout, level: :info)
     end
   end
+
+  # Configure Docker API with custom User-Agent
+  Docker.options ||= {}
+  Docker.options[:headers] ||= {}
+  Docker.options[:headers]["User-Agent"] = "tc-ruby/#{VERSION}"
 end

core/test/testcontainers_test.rb

@@ -1,7 +1,13 @@
 # frozen_string_literal: true
 
+require "test_helper"
+
 class TestcontainersTest < Minitest::Test
   def test_that_it_has_a_version_number
     refute_nil ::Testcontainers::VERSION
   end
+
+  def test_that_it_sets_user_agent_header
+    assert_equal "tc-ruby/#{::Testcontainers::VERSION}", Docker.options[:headers]["User-Agent"]
+  end
 end