Made a configurable constant

[RohitRathore1]

Why are these changes needed?

This modification ensure that the introduction message is easily configurable and can be changed without altering the method's logic directly.

Related issue number

Closes #1690

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

All modified and coverable lines are covered by tests ✅

Project coverage is 47.65%. Comparing base (b8ceb86) to head (d18bb6a).
Report is 42 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1819       +/-   ##
===========================================
+ Coverage   36.95%   47.65%   +10.69%     
===========================================
  Files          62       64        +2     
  Lines        6529     6837      +308     
  Branches     1447     1629      +182     
===========================================
+ Hits         2413     3258      +845     
+ Misses       3922     3310      -612     
- Partials      194      269       +75     

Flag	Coverage Δ
unittests	47.52% <100.00%> (+10.56%)	⬆️

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[JieyuZ2]

would it be better to make the intro msg an argument instead of configurable constant?

[RohitRathore1]

would it be better to make the intro msg an argument instead of configurable constant?

It would be a better option but as per issue I had opened my PR. @sonichi what do you think about the suggestion from @JieyuZ2? And other changes look good to me.

[sonichi]

would it be better to make the intro msg an argument instead of configurable constant?

It would be a better option but as per issue I had opened my PR. @sonichi what do you think about the suggestion from @JieyuZ2? And other changes look good to me.

@JieyuZ2 's suggestion can be addressed in a future PR if there are such needs.