Use permissions to restrict access instead of queryset

[dalmia]

Fixes #252

Test Plan

• Wrote tests
• Tested locally
• Tested on staging
• Tested on production
• If changes in DB, update DB schema and BigQuery (staging and prod)

[codecov]

Codecov Report

Merging #253 (78e0bc8) into master (883e656) will increase coverage by 0.03%.
The diff coverage is 97.95%.

@@            Coverage Diff             @@
##           master     #253      +/-   ##
==========================================
+ Coverage   96.92%   96.96%   +0.03%     
==========================================
  Files         143      143              
  Lines        2669     2668       -1     
==========================================
  Hits         2587     2587              
+ Misses         82       81       -1     

Impacted Files	Coverage Δ
plio/views.py	94.88% <90.00%> (+0.53%)	⬆️
plio/permissions.py	95.45% <100.00%> (ø)
plio/tests.py	100.00% <100.00%> (ø)

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[deepansh96]

I was not able to understand / forgot why this PR was needed and why the specified changes were made, please explain it to me on call