Configuration missing while D7 to D9 migration

1. +++ b/migrations/user_hash_settings.yml
   @@ -0,0 +1,17 @@
   +  source_module: user_hash
   

   I first thought this was unnecessary, but … it is necessary! This variable is from the user_hash module, and by default the variable plugin looks at variables from the system module.

   So … this makes perfect sense :)

2. +++ b/migrations/user_hash_settings.yml
   @@ -0,0 +1,17 @@
   +id: user_hash_settings
   +label: User hash configuration
   +migration_tags:
   +  - Drupal 7
   +  - Configuration
   

   The configuration for the user_hash module was not yet being migrated!

   Without these settings, it's impossible to correctly interpret the hashes … because you need to know the settings that generated them in order for the migrated values to make sense.

3. +++ b/src/Plugin/migrate/source/d7/UserHash.php
   @@ -8,7 +8,8 @@ use Drupal\migrate\Plugin\migrate\source\SqlBase;
     * @MigrateSource(
   - *   id = "d7_user_hash"
   + *   id = "d7_user_hash",
   + *   source_module = "user_hash"
     * )
   

   If you do not specify the source_module key, then the source plugin is available always, even when the user_hash module is not installed on the source site.

   IOW: if you install the user_hash module in Drupal 8 or 9 while running a migration, the absence of this key would cause a SQL error — because the hash column will not exist in the users table.

4. +++ b/src/Plugin/migrate/source/d7/UserHash.php
   @@ -20,7 +21,8 @@ class UserHash extends SqlBase {
      public function query() {
        $query = $this->select('users', 'u')
   -      ->fields('u', ['uid', 'hash']);
   +      ->fields('u', ['uid', 'hash'])
   +      ->condition('u.uid', 0, '>');
        return $query;
   

   Drupal core does not migrate user zero (the anonymous user). In Drupal 8|9, this is configuration, not an actual User entity.

   See \Drupal\user\Plugin\migrate\source\d7\User::query(), which also does:

     public function query() {
       return $this->select('users', 'u')
         ->fields('u')
         ->condition('u.uid', 0, '>');
     }
   

   As you can see: exactly the same condition!

   Without this added condition, the user_hash migration always reports one more row to migrate than there are users to migrate! 😨😅

Thanks for the patch @srishti.bankar and for the review @Wim Leers, just committet the changes and will publish a new release soon.