feat: add custom validation

[benediktziegler]

Description

This PR adds functionality to customise the commit message validation and to format the InvalidCommitMessageError to give better/more detailed feedback to the user.

Checklist

• Add test cases to all the changes you introduce
• Run ./scripts/format and ./scripts/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

The developer of a custom commitizen class can override the validate_commit_message and format_error_message methods to perform more complex commit message format checks then just a regex match and give more detailed feedback on failure.

Steps to Test This Pull Request

Run the the test_check_command_with_custom_validator_succeed and test_check_command_with_custom_validator_fail tests in test_check_command.py.

Additional context

This PR implements and fixes the comments from #648.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (v4-11-0@1d0f6cb). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff             @@
##             v4-11-0    #1236   +/-   ##
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  Coverage           ?   98.64%           
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  Files              ?       60           
  Lines              ?     2664           
  Branches           ?        0           
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  Hits               ?     2628           
  Misses             ?       36           
  Partials           ?        0           

Flag	Coverage Δ
unittests	98.64% <100.00%> (?)

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[benediktziegler]

@Lee-W I was wondering if you had any input to this PR?

[Lee-W]

I'll be mostly out till at least mid-Oct, will try to check in depth after that. Thanks!

[Lee-W]

Overall, I love this idea! left a few improvement suggestions

[Lee-W]

I'll be mostly out for the following month. Will try to take a look when I'm back.

[Lee-W]

Sorry for taking so long. Some nitpicks. but we're close to merge I think!

[Lee-W]

Hey @benediktziegler , I left a few nits, but overall this PR is great! We're super close to merging.
We'll include it in 4.11. Hopefully to release some time early Dec

[Lee-W]

Hey @benediktziegler , I think we're almost good to merge this one. But could you please help us rebase from the branch v4-11-0? I tried a bit, but I'm worried I might mess it up.

[benediktziegler]

@Lee-W I agree the merging was a bit messy and seems to even contain unwanted changes in the end. I propose I force push the squashed changes from this branch into this PR: https://github.com/benediktziegler/commitizen/tree/feature/custom-validation-clean instead.
Do you have any objections?

Or we merge this one instead: #1680

[Lee-W]

either way works perfect :) I'll take one final look at the other draft PR, if your force push didn't beat me haha

[benediktziegler]

Both are the same now, so I drop the draft PR.

Potential conflict with #1657.

[Lee-W]

Super! Thanks so much!