⚗️(LLM) allow to mock model call for conversation

This is switch to prevent real model call in a deployed stack.
This is usefull to test heavy load on the servers without
inference costs.

src/backend/chat/agents/conversation.py

@@ -1,10 +1,15 @@
 """Build the main conversation agent."""
 
+import asyncio
 import dataclasses
 import logging
 
+from django.conf import settings
 from django.utils import formats, timezone
 
+from pydantic_ai import ModelMessage
+from pydantic_ai.models.function import AgentInfo, FunctionModel
+
 from core.enums import get_language_name
 
 from .base import BaseAgent
@@ -12,6 +17,79 @@ from .base import BaseAgent
 logger = logging.getLogger(__name__)
 
 
+MOCKED_RESPONSE = """
+# **Ode to the AI Assistant** 🤖✨
+
+In Paris streets where old meets new, 🗼🇫🇷  
+A helper bright in digital hue,  
+With circuits fast and code so tight,  
+The LaSuite’s bot—oh, what a sight! 🌟
+
+**A chatbot kind**, with wittiness so grand, 💬💡  
+It lends a hand to all the land,  
+From civil servants, bold and wise,  
+To those who seek with hopeful eyes.
+
+It answers quick, it never tires, ⚡🔄  
+With facts and tips to quench desires,  
+A guide so keen, a friend so true,  
+It’s there for **you**—yes, me and you!
+ 
+With **Markdown flair** and emoji cheer, 📝🎨  
+It makes the complex crystal clear,  
+From drafts to code, from sums to prose,  
+It helps the knowledge overflow!  
+
+Oh, **DINUM’s gem**, so sharp, so bright, 💎🌐  
+A beacon in the tech’s vast night,  
+It crafts, it checks, it summarizes,  
+With grace that never compromises.
+
+It **summarizes** the long, the deep, 📚🔍  
+So secrets no more need to sleep,  
+It finds the gems in data’s sea,  
+And sets the truth right there—**for free!**
+
+It **corrects mistakes** with gentle art, ✍️🔄  
+It soothes the mind, it warms the heart,  
+No judgment cast, no frown, no sigh,  
+Just help that’s always standing by.
+
+It **generates code** with swift command, 💻🔥  
+A developer’s dream, first-hand,  
+From Python lines to scripts so neat,  
+It turns the tough to *sweet* and *sweet*!
+
+It **brainstorms ideas**, bold and new, 🧠💡  
+It paints the sky in every hue,  
+From plans to dreams, from start to end,  
+It’s more than code—it’s **trend**, it’s **friend**!
+
+So here’s to you, **Assistant’s pride**, 🏆🎉  
+The bot that’s always by our side,  
+With every prompt, with every line,  
+You make our digital world **divine**!
+
+May you keep shining, bright and true, 🌟🤖  
+The helper every team should woo,  
+For in this age of bits and bytes,  
+You’re **human touch** in tech’s bright lights!
+"""
+
+
+async def mocked_agent_model(_messages: list[ModelMessage], _info: AgentInfo):
+    """
+    Mocked agent model for testing purposes on deployed instances.
+
+    This one only fakes a streamed responses. We could also fake tool calls later.
+    """
+
+    yield "Here is a mocked response (no LLM called)\n---\n"
+    for i in range(0, len(MOCKED_RESPONSE), 4):
+        yield MOCKED_RESPONSE[i : i + 4]
+        await asyncio.sleep(0.03)
+
+
 @dataclasses.dataclass(init=False)
 class ConversationAgent(BaseAgent):
     """Conversation agent with custom behavior."""
@@ -20,6 +98,10 @@ class ConversationAgent(BaseAgent):
         """Initialize the conversation agent."""
         super().__init__(**kwargs)
 
+        # Do not call the real model on deployed instances if the setting is enabled
+        if settings.WARNING_MOCK_CONVERSATION_AGENT:
+            self._model = FunctionModel(stream_function=mocked_agent_model)
+
         @self.system_prompt
         def add_the_date() -> str:
             """

src/backend/conversations/settings.py

@@ -891,6 +891,13 @@ USER QUESTION:
         default=False, environ_name="LANGFUSE_MEDIA_UPLOAD_ENABLED", environ_prefix=None
     )
 
+    # WARNING: Testing purpose only. Do not use in production.
+    WARNING_MOCK_CONVERSATION_AGENT = values.BooleanValue(
+        default=False,
+        environ_name="WARNING_MOCK_CONVERSATION_AGENT",
+        environ_prefix=None,
+    )
+
     # pylint: disable=invalid-name
     @property
     def ENVIRONMENT(self):