Add ChatMessageHistory feature for multi-round dialogues in REST sessions (Issue #2284)

Co-Authored-By: Joe Moura <joao@crewai.com>

examples/chat_message_history_example.py

@@ -0,0 +1,48 @@
+from crewai import Agent, Task, Crew
+from crewai.memory import ChatMessageHistory, MessageRole
+
+# Create a chat message history
+chat_history = ChatMessageHistory()
+
+# Add some messages
+chat_history.add_human_message("Hello, I need help with a research task.")
+chat_history.add_ai_message("I'd be happy to help! What topic are you interested in?")
+chat_history.add_human_message("I'm interested in renewable energy technologies.")
+
+# Create an agent with access to the chat history
+researcher = Agent(
+    role="Renewable Energy Researcher",
+    goal="Provide accurate and up-to-date information on renewable energy technologies",
+    backstory="You are an expert in renewable energy with years of research experience.",
+    verbose=True,
+)
+
+# Create a task that uses the chat history
+research_task = Task(
+    description=(
+        "Review the conversation history and provide a detailed response about "
+        "renewable energy technologies, addressing any specific questions or interests."
+    ),
+    expected_output="A comprehensive response about renewable energy technologies.",
+    agent=researcher,
+)
+
+# Create a crew with memory enabled
+crew = Crew(
+    agents=[researcher],
+    tasks=[research_task],
+    verbose=True,
+    memory=True,
+)
+
+# Pass the chat history to the crew
+# In a real REST API scenario, you would store and retrieve this between requests
+crew_result = crew.kickoff(inputs={"chat_history": chat_history.get_messages_as_dict()})
+
+# Add the crew's response to the chat history
+chat_history.add_ai_message(str(crew_result))
+
+# Print the full conversation history
+print("\nFull Conversation History:")
+for message in chat_history.get_messages():
+    print(f"{message.role.value.capitalize()}: {message.content}")