[.Net]: Document: Improve function call and groupchat document

@ekzhu let's use this issue to discuss all the mode FunctionCallMiddleware should support?

What needs to be decided

The behavior of invoking a function call after inner agent generate a function call message, we should provide options to support the following scenarios
- private function call: invoke the function and send result back to inner agent to further generate reply but only return the last reply
- private function call with all function call history: invoke the function call and send result back to inner agent to generate further reply, and return all messages.
- directly return invoke result (The current implementation)

The current implementation of FunctionCallMiddleware

Overview

FunctionCallMiddleware is used to provide FunctionDefinition and invoke function call to an agent.

Usage

IAgent agent;
var functionCallMiddleware = new FunctionCallMiddleware(
    functions: [getWeatherFunctionDefinition], // provide list of function definitions to an agent to use
    functionMap: { getWeatherFunctionDefinition.Name, getWeatherWrapper } // the function map.
);

The current FunctionCallMiddleware has the following behavoirs according to whether functionMap is provided or not

when `functionMap` is not provided

In this situation, the agent respond will be returned "as is", even when it's a function call message.

sequenceDiagram
    actor User
    participant FunctionCallMiddleware(innerAgent)
    Note over FunctionCallMiddleware(innerAgent): [GetWeather]
    Note over FunctionCallMiddleware(innerAgent): functionMap: null
    User->>FunctionCallMiddleware(innerAgent): "Hello, what's the weather in Seattle?"
    create actor innerAgent
    FunctionCallMiddleware(innerAgent)->>innerAgent: "Hello, what's the weather in Seattle?"
    destroy innerAgent
    innerAgent->>FunctionCallMiddleware(innerAgent): "{FunctionName: GetWeather}"
    FunctionCallMiddleware(innerAgent)->>User: "{FunctionName: GetWeather}"

When functionMap is provided

If user sends a text message and inner agent returns a function call

In this situation, the FunctionCallMiddleware will invoke that function call and return result as text message as well.

sequenceDiagram
    actor User
    participant FunctionCallMiddleware(innerAgent)
    Note over FunctionCallMiddleware(innerAgent): [GetWeather]
    Note over FunctionCallMiddleware(innerAgent): functionMap: {GetWeatherFunc: lambda...}
    User->>FunctionCallMiddleware(innerAgent): "Hello, what's the weather in Seattle?" : TextMessage
    create actor innerAgent
    FunctionCallMiddleware(innerAgent)->>innerAgent: "Hello, what's the weather in Seattle?"
    destroy innerAgent
    innerAgent->>FunctionCallMiddleware(innerAgent): "{FunctionName: GetWeather}"
    FunctionCallMiddleware(innerAgent)->>FunctionCallMiddleware(innerAgent): Invoke GetWeatherFunc ...
    FunctionCallMiddleware(innerAgent)->>User: "{The result of GetWeatherFunc}" : TextMessage

If user sends a function call message

In this situation, the FunctionCallMiddleware will simply short-circuit the inner agent and return the invoke result as text message.

sequenceDiagram
    actor User
    participant FunctionCallMiddleware(innerAgent)
    Note over FunctionCallMiddleware(innerAgent): [GetWeather]
    Note over FunctionCallMiddleware(innerAgent): functionMap: {GetWeatherFunc: lambda...}
    User->>FunctionCallMiddleware(innerAgent): "{FunctionName: GetWeather}" : ToolCallMessage
    FunctionCallMiddleware(innerAgent)->>FunctionCallMiddleware(innerAgent): Short-curcuit the inner agent and Invoke GetWeatherFunc ...
    FunctionCallMiddleware(innerAgent)->>User: "{The result of GetWeatherFunc}" : ToolCallResultMessage

The new scenario `FunctionCallMiddleware` needs to support

private function call: inner agent use invoke result to further reply

sequenceDiagram
    actor User
    participant FunctionCallMiddleware(innerAgent)
    Note over FunctionCallMiddleware(innerAgent): [GetWeather]
    Note over FunctionCallMiddleware(innerAgent): functionMap: {GetWeatherFunc: lambda...}
    User->>FunctionCallMiddleware(innerAgent): "Hello, what's the weather in Seattle?" : TextMessage
    create actor innerAgent
    FunctionCallMiddleware(innerAgent)->>innerAgent: "Hello, what's the weather in Seattle?"
    loop: until inner agent reply with a non function call message
    innerAgent->>FunctionCallMiddleware(innerAgent): "{FunctionName: GetWeather}"
    FunctionCallMiddleware(innerAgent)->>innerAgent: "{FunctionCall Result}"
    end
    destroy innerAgent
    innerAgent->>FunctionCallMiddleware(innerAgent): "According to {xxx}, The weather in Seattle is sunny" : TextMessage
    FunctionCallMiddleware(innerAgent)->>User: "According to {xxx}, The weather in Seattle is sunny" : TextMessage

function call with all function call history: invoke the function call and send result back to inner agent to generate further reply, and return all messages.

sequenceDiagram
    actor User
    participant FunctionCallMiddleware(innerAgent)
    Note over FunctionCallMiddleware(innerAgent): [GetWeather]
    Note over FunctionCallMiddleware(innerAgent): functionMap: {GetWeatherFunc: lambda...}
    User->>FunctionCallMiddleware(innerAgent): "Hello, what's the weather in Seattle?" : TextMessage
    create actor innerAgent
    FunctionCallMiddleware(innerAgent)->>innerAgent: "Hello, what's the weather in Seattle?"
    loop: until inner agent reply with a non function call message
    innerAgent->>FunctionCallMiddleware(innerAgent): "{FunctionName: GetWeather}"
    FunctionCallMiddleware(innerAgent)->>innerAgent: "{FunctionCall Result}"
    end
    destroy innerAgent
    innerAgent->>FunctionCallMiddleware(innerAgent): "According to {xxx}, The weather in Seattle is sunny" : TextMessage
    FunctionCallMiddleware(innerAgent)->>User: [...function call history, "According to {xxx}, The weather in Seattle is sunny"] : AggregateMessage

microsoft / autogen