ENG-4454 - Make Feature Flag for HRIS to allow bulk import

- tags :: 15Five Jira Namely Integration BambooHR Integration

Description

Similar to the need for a feature flag to allow bulk import when SCIM is enabled (which we currently have), we should also have a feature flag (in django) to allow for bulk import when BambooHR or Namely is enabled. This helps customers manage certain groups that are not importing over from 15Five.

Example 1: Customer wants to exclude contractors from Reviews, but wants them in 15Five. To do this, they want to export a BambooHR CSV or Namely and upload into 15Five. This cannot be done currently.

Example 2: Customer using HRIS wants to use custom attributes. Allowing them to update this information alongside their recurring HRIS syncs would allow them to import custom attributes prior to any work we do in our HRIS Import improvements, which might be months away.

Development Notes

1. There is a similar feature for SCIM called FeatureName.SCIM__ALLOW_CSV_IMPORT

2. On BambooHRExternalIdentityManagementService and its Namely counterpart there should be an allows_bulk_import property, like the one implemented in SCIMExternalIdentityManagementService