fix: Register DynamoAI guardrail initializer and enum entry

Fix the "Unsupported guardrail: dynamoai" error by:
1. Adding DYNAMOAI to SupportedGuardrailIntegrations enum
2. Implementing initialize_guardrail() and registries in dynamoai/__init__.py

The DynamoAI guardrail was added in PR #15920 but never properly registered
in the initialization system. The __init__.py was missing the
guardrail_initializer_registry and guardrail_class_registry dictionaries
that the dynamic discovery mechanism looks for at module load time.

Fixes #22773

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

litellm/proxy/guardrails/guardrail_hooks/dynamoai/__init__.py

@@ -1,3 +1,34 @@
+from typing import TYPE_CHECKING
+
+from litellm.types.guardrails import SupportedGuardrailIntegrations
+
 from .dynamoai import DynamoAIGuardrails
 
-__all__ = ["DynamoAIGuardrails"]
+if TYPE_CHECKING:
+    from litellm.types.guardrails import Guardrail, LitellmParams
+
+
+def initialize_guardrail(litellm_params: "LitellmParams", guardrail: "Guardrail"):
+    import litellm
+    from litellm.proxy.guardrails.guardrail_hooks.dynamoai import DynamoAIGuardrails
+
+    _dynamoai_callback = DynamoAIGuardrails(
+        api_base=litellm_params.api_base,
+        api_key=litellm_params.api_key,
+        guardrail_name=guardrail.get("guardrail_name", ""),
+        event_hook=litellm_params.mode,
+        default_on=litellm_params.default_on,
+    )
+    litellm.logging_callback_manager.add_litellm_callback(_dynamoai_callback)
+
+    return _dynamoai_callback
+
+
+guardrail_initializer_registry = {
+    SupportedGuardrailIntegrations.DYNAMOAI.value: initialize_guardrail,
+}
+
+
+guardrail_class_registry = {
+    SupportedGuardrailIntegrations.DYNAMOAI.value: DynamoAIGuardrails,
+}

litellm/types/guardrails.py

@@ -44,6 +44,7 @@ guardrails:
 class SupportedGuardrailIntegrations(Enum):
     APORIA = "aporia"
     BEDROCK = "bedrock"
+    DYNAMOAI = "dynamoai"
     GUARDRAILS_AI = "guardrails_ai"
     LAKERA = "lakera"
     LAKERA_V2 = "lakera_v2"