Issue #2559345 by lostkangaroo, phenaproxima, benjy, neclimdul: Document...

Issue #2559345 by lostkangaroo, phenaproxima, benjy, neclimdul: Document source_provider and minimum_schema_version annotation properties

core/modules/migrate/src/Annotation/MigrateSource.php

@@ -45,4 +45,30 @@ class MigrateSource extends Plugin {
    */
   public $requirements_met = TRUE;
 
+  /**
+   * Identifies the system providing the data the source plugin will read.
+   *
+   * This can be any type, and the source plugin itself determines how the value
+   * is used. For example, Migrate Drupal's source plugins expect
+   * source_provider to be the name of a module that must be installed and
+   * enabled in the source database.
+   *
+   * @see \Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase::checkRequirements
+   *
+   * @var mixed
+   */
+  public $source_provider;
+
+  /**
+   * Specifies the minimum version of the source provider.
+   *
+   * This can be any type, and the source plugin itself determines how it is
+   * used. For example, Migrate Drupal's source plugins expect this to be an
+   * integer representing the minimum installed database schema version of the
+   * module specified by source_provider.
+   *
+   * @var mixed
+   */
+  public $minimum_version;
+
 }