Filter out those facilities that are already linked to user

[Pranshu1902]

Proposed Changes

• Filter out those facilities that are already linked to the user. When the Link Facility page makes a call to the backend, if the username is passed then the backend will filter out those facilities that are already linked.

Associated Issue

Fixes #1581

Merge Checklist

• Tests added/fixed
• Update docs in /docs
• Linting Complete
• Any other necessary step

Only PR's with test cases included and passing lint and test pipelines will be reviewed

@coronasafe/care-backend-maintainers @coronasafe/care-backend-admins

[nihal467]

@Pranshu1902 fix the failed test

[nihal467]

@Pranshu1902 the test is still failing

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (5dff7a0) 59.44% compared to head (81ea749) 60.01%.
Report is 8 commits behind head on master.

❗ Current head 81ea749 differs from pull request most recent head 09792a2. Consider uploading reports for the commit 09792a2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1588      +/-   ##
==========================================
+ Coverage   59.44%   60.01%   +0.57%     
==========================================
  Files         208      208              
  Lines       11278    11330      +52     
  Branches     1597     1608      +11     
==========================================
+ Hits         6704     6800      +96     
+ Misses       4372     4305      -67     
- Partials      202      225      +23     

Files	Coverage Δ
care/facility/api/viewsets/facility.py	61.94% <54.54%> (-0.80%)	⬇️

... and 17 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[nihal467]

@sainak review the backend, the functionality looks good to me

[rithviknishad]

@Pranshu1902 are you sure pre-commit lint is working fine in your local?

Check the lint CI

[nihal467]

tested locally, looks good to me @vigneshhari can you review it