Add ability to import child and parent relationship

[crisr15]

Summary

The UCSC data uses many child and parent relationships. Enable child parent relationships in the CSV parser.

Acceptance Criteria

• [x] Relationships can be imported using the parent CSV column
• [x] Relationships can be imported using Bulkrax identifiers (bulkrax_identifier column)
• [x] Relationships can be imported using IDs¹
• Multiple relationships can be defined on a single record by:
  • [x] Splitting values with a pipe character (|)
  • [x] Adding a numerated suffix to the column header (i.e. parent_1, parent_2)
• [x] A Collection can be made a parent of a Work
• [x] A Collection can be made a parent of a Collection
• [x] A Work can be made a parent of a Work
• [x] A Work cannot be made a parent of a Collection

¹ To test this, create a Collection and Work through the UI and use their IDs in the CSV

Testing Instructions

For additional information re: importing relationships, refer to the Bulkrax documentation

1. Download this CSV²: i3_qa_2_edit.csv
2. Login as an admin
3. Navigate to Dashboard --> Importers --> New
4. Fill out all of the importer's required fields. Upload the file from Step 1. Click "Create and Import"
5. After no more than 3 minutes (assuming no other importers are running), check to see if the records were created with the proper relationships using the Acceptance Criteria

² This CSV should satisfy most of the Acceptance Criteria, but will require changes to test the following acceptance criteria:

• Relationships can be imported using IDs¹
• Multiple relationships can be defined on a single record by... Adding a numerated suffix to the column header (i.e. parent_1, parent_2)

Additional Information

PR in client's repo: https://github.com/UCSCLibrary/ucsc-library-digital-collections/pull/219