Fixes #920 and #764. Resolved MVDkeyError in Stripe token

[Nandika-A]

This error (issue #920 and issue #764) was raised due to a network connection problem (occurs rarely) between the stripe and the server, hence the token was not getting generated. Solutions are mentioned in stripe's documentation.
This is fixed by exception handling. Now it displays the following message instead of giving an error:

Idempotency keys are also added while creating a customer, to recover from connection error. UUID V4 is used to generate a string that could be used as Idempotency key, as mentioned in the documentation.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (a689641) 81.02% compared to head (495ec16) 80.95%.
Report is 3 commits behind head on main.

❗ Current head 495ec16 differs from pull request most recent head 0e1e389. Consider uploading reports for the commit 0e1e389 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #938      +/-   ##
==========================================
- Coverage   81.02%   80.95%   -0.08%     
==========================================
  Files          95       95              
  Lines        2862     2867       +5     
  Branches      269      270       +1     
==========================================
+ Hits         2319     2321       +2     
- Misses        492      494       +2     
- Partials       51       52       +1     

Files	Coverage Δ
donations/views.py	64.58% <40.00%> (-2.86%)	⬇️

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a689641...0e1e389. Read the comment docs.

[amakarudze]

Thanks for your work on this @Nandika-A, can you add tests for the lines you added so coverage passes?

[Nandika-A]

Thanks for your work on this @Nandika-A, can you add tests for the lines you added so coverage passes?

Ya sure!

[Nandika-A]

Thanks for the review @amakarudze! I have added the tests. The test checks if the view redirects to the error page and if the expected session variable is set with the correct error message. Could you please check it now?