fix: create group support multiple csv files

[marlonkeating]

Jira Ticket

This change fixes some bugs in the behavior of uploading csv lists of enterprise members to add to a new group.

Testing Instructions

• Go to the admin-portal repo, pull down branch, and run npm run start:stage
• Navigate to https://localhost.stage.edx.org:1991/alc-general/admin/people-management
• Click 'Create group'
• Upload csv file containing enterprise members
• Click check box next to one of the added members, and click 'Remove'
• Upload same csv file again
• Verify the removed member was re-added

For all changes

• Ensure adequate tests are in place (or reviewed existing tests cover changes)

Only if submitting a visual change

• Ensure to attach screenshots
• Ensure to have UX team confirm screenshots

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.44%. Comparing base (a95d20f) to head (77ed2af).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1419      +/-   ##
==========================================
- Coverage   86.44%   86.44%   -0.01%     
==========================================
  Files         660      660              
  Lines       14929    14923       -6     
  Branches     3168     3163       -5     
==========================================
- Hits        12906    12900       -6     
  Misses       1951     1951              
  Partials       72       72              

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[jesperhodge]

Great job, seems to work well, and I love the straightforward code you wrote. I just recommended adding one more test but otherwise everything super.

[jesperhodge]

I love the simplification. Having a useEffect that is triggered by an input change is an antipattern that creates problems, like in the bug I was working on. It's great that you just introduce a simpler function that is called directly.