dkan:harvest:register should check for required fields rather than throw exception

[paul-m]

Current Behavior

Trying to register a harvest plan without an identifier looks like this:

% ddev drush dkan:harvest:register --extract-uri https://example.com/path/harvest.json
 [error]  Drupal\Core\Database\IntegrityConstraintViolationException: SQLSTATE[HY000]: General error: 1364 Field 'id' doesn't have a default value: INSERT INTO "harvest_plans" ("data") VALUES (:db_insert_placeholder_0); Array
(
    [:db_insert_placeholder_0] => {"identifier":"","extract":{"type":"Harvest\\ETL\\Extract\\DataJson","uri":"https://example.com/path/harvest.json"},"transforms":[],"load":{"type":"Drupal\\harvest\\Load\\Dataset"}}
)
 in Drupal\mysql\Driver\Database\mysql\ExceptionHandler->handleExecutionException() (line 45 of /var/www/html/docroot/core/modules/mysql/src/Driver/Database/mysql/ExceptionHandler.php). 
 [error]  SQLSTATE[HY000]: General error: 1364 Field 'id' doesn't have a default value: INSERT INTO "harvest_plans" ("data") VALUES (:db_insert_placeholder_0); Array
(
    [:db_insert_placeholder_0] => {"identifier":"","extract":{"type":"Harvest\\ETL\\Extract\\DataJson","uri":"[https:\/\/download.cms.gov\/openpayments\/staging\/2025JAN\/summary_entities_hidden.json](https://example.com/path/harvest.json)"},"transforms":[],"load":{"type":"Drupal\\harvest\\Load\\Dataset"}}
)

This is confusing and not helpful.

Expected Behavior

Since the --identifier parameter is basically required, we should ensure that it exists, rather than allow a PDO error to tell us.

Steps To Reproduce

Try to register a harvest without an identifier.

Relevant log output (optional)

No response

Anything else?

No response

[dafeder]

Just noting that there's some overlap here with #3329