perf(api): share cached provider-type choices across filters and serializer

- Move get_provider_type_choices into a leaf module so the provider
  serializer field reuses the filters' cached list instead of recomputing
  SDK provider discovery on every request

api/src/backend/api/filters.py

@@ -1,5 +1,4 @@
 from datetime import date, datetime, timedelta, timezone
-from functools import lru_cache
 
 from dateutil.parser import parse
 from django.conf import settings
@@ -67,19 +66,8 @@ from api.uuid_utils import (
     uuid7_range,
     uuid7_start,
 )
+from api.provider_types import get_provider_type_choices
 from api.v1.serializers import TaskBase
-from prowler.providers.common.provider import Provider as SDKProvider
-
-
-@lru_cache(maxsize=1)
-def get_provider_type_choices():
-    """Provider-type filter choices driven by the SDK's available providers
-    instead of a static enum, so filtering covers external providers too.
-
-    Cached because the installed providers are fixed for the process lifetime
-    and provider-type filters live on hot list endpoints.
-    """
-    return [(name, name) for name in SDKProvider.get_available_providers()]
 
 
 class CustomDjangoFilterBackend(DjangoFilterBackend):

api/src/backend/api/provider_types.py

@@ -0,0 +1,15 @@
+from functools import lru_cache
+
+from prowler.providers.common.provider import Provider as SDKProvider
+
+
+@lru_cache(maxsize=1)
+def get_provider_type_choices():
+    """Provider-type choices from the SDK's available providers, so they cover
+    external providers and not just a static enum.
+
+    Cached for the process lifetime; hot-installing a provider needs
+    coordinated cache invalidation (tracked separately) to show up here without
+    a restart. Shared by the filters and the provider serializer.
+    """
+    return [(name, name) for name in SDKProvider.get_available_providers()]

api/src/backend/api/v1/serializers.py

@@ -71,9 +71,9 @@ from api.v1.serializer_utils.lighthouse import (
     OpenAICredentialsSerializer,
 )
 from api.v1.serializer_utils.processors import ProcessorConfigField
+from api.provider_types import get_provider_type_choices
 from api.v1.serializer_utils.providers import ProviderSecretField
 from prowler.lib.mutelist.mutelist import Mutelist
-from prowler.providers.common.provider import Provider as SDKProvider
 
 # Base
 
@@ -855,12 +855,9 @@ class ProviderGroupMembershipSerializer(RLSSerializer, BaseWriteSerializer):
 # Providers
 class ProviderEnumSerializerField(serializers.ChoiceField):
     def __init__(self, **kwargs):
-        # The SDK is the source of truth for which providers exist, so the
-        # accepted values track the installed providers (built-in or external)
-        # instead of a static enum.
-        kwargs["choices"] = [
-            (name, name) for name in SDKProvider.get_available_providers()
-        ]
+        # Accepted values track the SDK's installed providers (built-in or
+        # external), shared with the filters via one cached source.
+        kwargs["choices"] = get_provider_type_choices()
         super().__init__(**kwargs)