Ignore AppConfig[:limit_csv_fields] unless the params[:dt] == 'csv'

[martinlovell]

Ignore the AppConfig[:limit_csv_fields] value unless the request type is csv

Description

The AppConfig[:limit_csv_fields] property causes the Search model to ignore the fields parameter. This causes all fields to be returned from the query. The AppConfig[:limit_csv_fields] should limit the fields returned by the search only when dt=xml. This change allows a JSON search to limit the number of fields returned when the app is configured with AppConfig[:limit_csv_fields] = false.

Related JIRA Ticket or GitHub Issue

https://archivesspace.atlassian.net/browse/ANW-1975

How Has This Been Tested?

I added four tests to model_search_test.rb to ensure that the fl parameter is sent to SOLR appropriately based on AppConfig[:limit_csv_fields] and the dt parameter.

Screenshots (if appropriate):

n/a

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• I have authority to submit this code.
• I have added tests to cover my changes.
• All new and existing tests passed.

[brianzelip]

Thanks @martinlovell -- we'll have a look and follow up here.