Use dkan_allowed_extensions() during harvest

[rhabbachi]

connects #2577

Description.

The dkan_allowed_extensions() function (added in #2664 is the way to go when overriding resources allowed extensions. During a harvest a check on the allowed extensions is done to honor the user setting. This PR will update this check (done in HarvestMigration::prepareResourceHelper) to use dkan_allowed_extensions() instead of querying the field settings.

How to reproduce

Step-by-step instructions for reproducing the bug:

1. Add harvest source that have resources with extensions that are not part of the default field setting but allowed via the dkan_allowed_extensions().
2. Run Harvest on the source.

Expected:
All the resources are harvested and imported correctly.

Currently:
Resources with non default extensions introduced via dkan_allowed_extensions() fail to be harvested.

QA Steps

1. Add harvest source that have resources with extensions that are not part of the default field setting.
2. Make sure to allowed the non default extension via the dkan_allowed_extensions() mechanism.
3. Run Harvest on the source.

The Harvest should proceed without issues.

Merge process

• N/A

Reminders

• There is test for the issue.
• Coding standards checked.
• Review docs.getdkan.com (or in /docs) to see if it still covers the scope of the PR and update if needed.

[rhabbachi]

I suspect that this PR can be connected to #2577

[janette]

Thank you @rhabbachi it works!