Add a button to Time Entry admin to synchronise ProCAT

[dalonsoa]

Description

It helps when I want to manually ensure that ProCAT and Clockify are in sync, also serving for diagnosis and debugging. As it is now, I need to get into the server and manually add the tasks. This PR also illustrates how to add functionality to the Django Admin in an easy way, when we do not want to create dedicated public facing views.

Fixes #630

How to test

• Launch the app with docker compose up
• Go to the Admin -> Time Entries and check there is a bottom at the top to Synchronise with Clockify
• Make sure there is a user with a valid email (eg. your own)
• Add a project with all the bits and pieces required for it to be Active
• Add it the Clockify ID of an existing project you have worked on recently, just for testing purposes
• Clicking the new button in the Admin should bring whatever entries you have log in Clockify for this project ID within the last 30 days
• If it does not work, there should be a message indicating so and the logs should show the problem

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature (non-breaking change which adds functionality)
• Optimization (non-breaking, back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Key checklist

• All tests pass (eg. python -m pytest)
• The documentation builds and looks OK (eg. mkdocs serve)
• Pre-commit hooks run successfully (eg. pre-commit run --all-files)

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added or an issue has been opened to tackle that in the future. (Indicate issue here: # (issue))

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.28%. Comparing base (f87990a) to head (55a100e).

Files with missing lines	Patch %	Lines
main/admin.py	64.28%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #649      +/-   ##
==========================================
- Coverage   92.53%   92.28%   -0.26%     
==========================================
  Files          50       50              
  Lines        1473     1490      +17     
  Branches      112      113       +1     
==========================================
+ Hits         1363     1375      +12     
- Misses         92       97       +5     
  Partials       18       18              

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