Add show user block api endpoint

test/controllers/api/user_blocks_controller_test.rb

@@ -0,0 +1,26 @@
+require "test_helper"
+
+module Api
+  class UserBlocksControllerTest < ActionDispatch::IntegrationTest
+    def test_routes
+      assert_routing(
+        { :path => "/api/0.6/user_blocks/1", :method => :get },
+        { :controller => "api/user_blocks", :action => "show", :id => "1" }
+      )
+    end
+
+    def test_show
+      block = create(:user_block)
+
+      get api_user_block_path(:id => block)
+      assert_response :success
+      assert_select "user_block[id='#{block.id}']", 1
+    end
+
+    def test_show_not_found
+      get api_user_block_path(:id => 123)
+      assert_response :not_found
+      assert_equal "text/plain", @response.media_type
+    end
+  end
+end