feat(flagd): RPC resolver substitutes caller default on reason=DISABLED

Mirrors the existing reason=DEFAULT substitution: when the server returns an empty variant alongside DISABLED, surface the caller's code default value rather than the zero proto value.

Signed-off-by: Todd Baert <todd.baert@dynatrace.com>

Author: toddbaert

providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/resolvers/grpc.py

@@ -443,8 +443,9 @@ def _resolve(  # noqa: PLR0915 C901
             raise GeneralError(message) from e
 
         # When no default variant is configured, the server returns an empty/zero proto
-        # value with reason=DEFAULT. In that case, return the caller's code default value.
-        if response.reason == Reason.DEFAULT and not response.variant:
+        # value with reason=DEFAULT. For DISABLED flags the server omits the variant too.
+        # In both cases, return the caller's code default value.
+        if response.reason in (Reason.DEFAULT, Reason.DISABLED) and not response.variant:
             value = default_value
 
         # Got a valid flag and valid type. Return it.