Refactoring task cache to be a tool (#50)

* Refactoring task cache to be a tool

The previous implementation of the task caching system was early exiting
the agent executor due to the fact it was returning an AgentFinish object.

This now refactors it to use a cache specific tool that is dynamically
added and forced into the agent in case of a task execution that was
already executed with the same input.

crewai/agents/tools_handler.py

@@ -2,6 +2,7 @@ from typing import Any, Dict
 
 from langchain.callbacks.base import BaseCallbackHandler
 
+from ..tools.cache_tools import CacheTools
 from .cache_handler import CacheHandler
 
 
@@ -35,8 +36,9 @@ class ToolsHandler(BaseCallbackHandler):
             and "Invalid or incomplete response" not in output
             and "Invalid Format" not in output
         ):
-            self.cache.add(
-                tool=self.last_used_tool["tool"],
-                input=self.last_used_tool["input"],
-                output=output,
-            )
+            if self.last_used_tool["tool"] != CacheTools().name:
+                self.cache.add(
+                    tool=self.last_used_tool["tool"],
+                    input=self.last_used_tool["input"],
+                    output=output,
+                )