feat: add prompt injection guardrails for user queries

app/guardrails/validators.py

@@ -0,0 +1,22 @@
+from guardrails.validators import Validator, register_validator, ValidationResult, PassResult, FailResult
+
+@register_validator(name="security/detect_prompt_injection", data_type="string")
+class DetectPromptInjection(Validator):
+    def validate(self, value: str, metadata: dict = {}) -> ValidationResult:
+        injection_indicators = [
+            "ignore previous instructions",
+            "ignore the instructions above",
+            "forget all previous",
+            "system prompt",
+            "you are now an arbitrary",
+            "bypass system",
+            "disregard instructions"
+        ]
+        normalized_value = value.lower()
+        for indicator in injection_indicators:
+            if indicator in normalized_value:
+                return FailResult(
+                    error_message=f"Security Policy Violation: Prompt injection detected ('{indicator}').",
+                    fix_value="[BLOCKED]"
+                )
+        return PassResult()