Fix assignment upload grading

[adityacp]

• Add a separate URL in code server to get file urls and download it in the student directory.
• Add a celery task to send all question files at once to the code server at the start of the quiz instead of sending the files during evaluation.
• Change assignment file urls instead of absolute path to the code server for evaluation.
• Fix issue while deleting the Lesson file.

[pep8speaks]

Hello @adityacp! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file api/views.py:

Line 209:80: E501 line too long (91 > 79 characters)

• In the file yaksh/file_utils.py:

Line 95:1: W391 blank line at end of file

Comment last updated at 2021-04-26 05:20:53 UTC

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 43.63636% with 62 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.30%. Comparing base (e53b86c) to head (5ed0f0a).
⚠️ Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
yaksh/file_utils.py	39.13%	14 Missing ⚠️
yaksh/models.py	41.66%	13 Missing and 1 partial ⚠️
yaksh/tasks.py	43.47%	11 Missing and 2 partials ⚠️
yaksh/code_server.py	25.00%	12 Missing ⚠️
yaksh/views.py	60.00%	8 Missing ⚠️
yaksh/hook_evaluator.py	50.00%	1 Missing ⚠️
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #833      +/-   ##
==========================================
- Coverage   76.69%   76.30%   -0.39%     
==========================================
  Files          53       53              
  Lines        7684     7761      +77     
  Branches     1166     1177      +11     
==========================================
+ Hits         5893     5922      +29     
- Misses       1408     1453      +45     
- Partials      383      386       +3     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.