Source plugins must define the source_module property

Problem/Motivation

While using source plugins, e.g. url this error is thrown

In MigrationPluginManager.php line 104
The url plugin must define the source_module property.

Steps to reproduce

Use as source like

source:
  plugin: url
  data_fetcher_plugin: file
  data_parser_plugin: json

Then drush ms

Proposed resolution

Add the source_module annotation.