Better agent execution error handling (#54)

A few quality of life improvements around cache handling and repeated tool usage

crewai/agents/cache/cache_handler.py

@@ -0,0 +1,20 @@
+from typing import Optional
+
+from pydantic import PrivateAttr
+
+
+class CacheHandler:
+    """Callback handler for tool usage."""
+
+    _cache: PrivateAttr = {}
+
+    def __init__(self):
+        self._cache = {}
+
+    def add(self, tool, input, output):
+        input = input.strip()
+        self._cache[f"{tool}-{input}"] = output
+
+    def read(self, tool, input) -> Optional[str]:
+        input = input.strip()
+        return self._cache.get(f"{tool}-{input}")