Some post_import messages should not be errors

[paul-m]

The problem we're trying to solve:

The user might see a lot of errors during post-processing, for resources which don't have data dictionaries.

It's totally OK for resources to not have data dictionaries associated with them, so it should not be an error. However, it should show up in an import log and the import status dashboard because this still might be unexpected... The user might think the resource should have a data dictionary.

Our solution:

• Introduces a new exception called ResourceDoesNotHaveDictionary. This is thrown when DictionaryEnforcer can't find a dictionary for the given resource. This allows us to handle this situation differently than a generic Exception.
• PostImportResourceProcessor now handles the ResourceDoesNotHaveDictionary exception as a special case, so it can tell the user that it couldn't find a dictionary for that resource.
• Modify tests to reflect these situations and prevent regressions.

QA:

• Set the DKAN site to use 'Distribution reference' data dictionaries.
• Import datasets with no associated data dictionaries.
• Verify that no errors are thrown during the post_import phase, but instead an informative message is displayed.

Helpful script:

ddev dkan-site-install
ddev drush pm-enable sample_content
ddev drush dkan:sample-content:create
ddev drush config:set metastore.settings data_dictionary_mode reference
ddev drush cron
ddev drush cron

You should see messages like this:

 [notice] No data-dictionary found for resource with id "0310f6c2d28bbee5de1211e5b5bb0b1c" and version "1721843317".

You should then also see a message like this in the dataset import status dashboard:

done Resource 0310f6c2d28bbee5de1211e5b5bb0b1c does not have a data dictionary.

[dafeder]

A lot of these tests were long overdue, thanks @paul-m!