Added Search_Shopcart_by_User_id

[pr-2310]

Made the following changes:

• Added find_by_user_id method
• Added search shopcart by user_id endpoint in routes.py
• Added testcases for search shopcart by user_id

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.61%. Comparing base (40f2465) to head (5f35ced). Report is 4 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #64 +/- ## ========================================== - Coverage 95.82% 95.61% -0.22% ========================================== Files 11 11 Lines 407 433 +26 ========================================== + Hits 390 414 +24 - Misses 17 19 +2 ```

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[carolinetfls]

One check is failed which shows the test coverage has gone done. Please fix it then restart a pull request

[carolinetfls]

to fix