[.Net] Support graph group chat by adding workflow and transition.

[LittleLittleCloud]

Why are these changes needed?

This PR enables graph group chat in AutoGen.Net by adding a Workflow and Transition class.

Transition

Transition represents a transit step from one agent to another. To create a Transition, using Transition.Create

Transition also conditionally accepts a lambda function which determines if it's enable or not. This allows workflow to be dynamically adjusted based on conversation. (Inspired by the Workflow in PROSE.Conversations)

var alice = new EchoAgent("alice");
var bob = new EchoAgent("bob");

// create a transition that is enabled in all situation.
var aliceToBob = Transition.Create(alice, bob);

// create a transition that is enabled only when conversation satisfy a certain condition
var aliceToBobWhenMessageIsHello = Transition.Create(alice, bob, async (from, to, messages) =>
{
    if (messages.Any(m => m is { Content: "Hello" }))
    {
        return true;
    }

    return false;
});

Workflow

Workflow is essentially a list of Transition. The next transabled candidates from one agent can be retrieved by TransitToNextAvailableAgentsAsync API

To create a workflow

var alice = new EchoAgent("alice");
var bob = new EchoAgent("bob");
var charlie = new EchoAgent("charlie");

// alice can speak to bob
// bob can speak to charlie
// charlie can speak to alice
var aliceToBob = Transition.Create(alice, bob);
var bobToCharlie = Transition.Create(bob, charlie);
var charlieToAlice = Transition.Create(charlie, alice);
var workflow = new Workflow([aliceToBob, bobToCharlie, charlieToAlice]);

var nextAgents = await workflow.TransitToNextAvailableAgentsAsync(alice , []); // nextAgents will be [bob]

Consume workflow in group chat

The group chat now supports workflow. In SelectNextSpeaker function, the group chat will first retrieve the available candidates based on current agent and work flow, then use admin to intelligently decide the next speaker.
To consume a workflow in group chat, simply pass it when creating the group

var groupChat = new GroupChat(
   workflow: workflow,
   ...);

Example

checkout Example04_Dynamic_GroupChat_Coding_Task which is accommodated to groupchat with workflow

Related issue number

Resolve #1648

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 ✅

Comparison is base (1e07f47) 39.35% compared to head (f3570cf) 39.12%.

Additional details and impacted files

@@            Coverage Diff             @@
##           dotnet    #1761      +/-   ##
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- Coverage   39.35%   39.12%   -0.24%     
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  Files          57       57              
  Lines        6093     6173      +80     
  Branches     1362     1383      +21     
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+ Hits         2398     2415      +17     
- Misses       3499     3564      +65     
+ Partials      196      194       -2     

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[joshkyh]

Thanks for the invite to review. I don't code in .net so I might be wrong here, I think the current functionalities only support the provision of Allowed Transitions. I'm not sure if you meant to fully translate the Python functionalities which could be missing here in .net.

1. Support the input of Disallowed Transitions.
2. Transitions validations and raising warnings where appropriate?

[LittleLittleCloud]

@joshkyh

Overall, it's not the goal of this PR to fully transfer what python autogen graph chat has to dotnet one. And there'll be a little difference in api design and implementation because of difference in ecosystem and language syntax.