Min tokens in token limiter

[giorgossideris]

Why are these changes needed?

A min_tokens_threshold is added to MessageTokenLimiter, which gives the option to cut tokens only after the specified message limit is reached.

Related issue number

Closes #2306.

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 17 lines in your changes are missing coverage. Please review.

Project coverage is 33.50%. Comparing base (ded2d61) to head (6b05ab3).
Report is 7 commits behind head on main.

Files	Patch %	Lines
...togen/agentchat/contrib/capabilities/transforms.py	0.00%	17 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2400      +/-   ##
==========================================
+ Coverage   33.33%   33.50%   +0.17%     
==========================================
  Files          83       81       -2     
  Lines        8636     8741     +105     
  Branches     1835     1868      +33     
==========================================
+ Hits         2879     2929      +50     
- Misses       5516     5564      +48     
- Partials      241      248       +7     

Flag	Coverage Δ
unittests	33.50% <0.00%> (+0.17%)	⬆️

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[WaelKarkoub]

@giorgossideris Thanks for the PR! min_tokens_threshold makes sense for MessageTokenLimiter. Like we discussed before, MessageHistoryLimiter shouldn't concern itself with the number of tokens to avoid overlap in responsibilities.

[WaelKarkoub]

PR is shaping up nicely

[WaelKarkoub]

Just a reminder to update the guide and notebook

[giorgossideris]

@WaelKarkoub I made the discussed changes, although there are two points that concern me:

1. About the min_tokens < max_tokens condition: what if the user wants to set min_tokens to the max token limit of the model?
2. (Not really related to this PR) Notebook and website docs are not aligned (same idea but different structure). I am not sure if this is something that we want to avoid.

[WaelKarkoub]

Thank you for the changes! A couple more looks and this is mergeable.

1. Your current validator makes sense. min_tokens <= max_tokens
2. No need for a major rewrite, just a simple demonstration of how min_tokens works is enough

[giorgossideris]

@WaelKarkoub I made the requested changes.

[WaelKarkoub]

Thanks, looks good!

[gitguardian]

⚠️ GitGuardian has uncovered 5 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secrets in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
-		Generic High Entropy Secret	899c472	test/oai/test_utils.py	View secret
-		Generic CLI Secret	df20e0b	.github/workflows/dotnet-release.yml	View secret
-		Generic High Entropy Secret	899c472	test/oai/test_utils.py	View secret
-		Generic High Entropy Secret	899c472	test/oai/test_utils.py	View secret
-		Generic High Entropy Secret	899c472	test/oai/test_utils.py	View secret

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[giorgossideris]

Hello @ekzhu, do you want me to do anything related to the failed test?