Fix: Python 3.9 compatibility

- Remove slots=True from dataclasses (Python 3.10+ feature)
- Add eval-type-backport dependency for union type annotations on Python 3.9

Author: loookashow

pyproject.toml

@@ -29,6 +29,7 @@ dependencies = [
   "pydantic>=2.6",
   "cryptography>=42.0.0",
   "typing-extensions>=4.8",
+  "eval-type-backport>=0.2.0; python_version < '3.10'",
 ]
 
 [project.optional-dependencies]

src/foxnose_sdk/auth/base.py

@@ -6,7 +6,7 @@
 from ..errors import FoxnoseAuthError
 
 
-@dataclass(frozen=True, slots=True)
+@dataclass(frozen=True)
 class RequestData:
     """Immutable view of the outbound request used when applying auth."""
 

src/foxnose_sdk/auth/jwt.py

@@ -13,7 +13,7 @@ def get_token(self) -> str:
         """Return the latest access token string."""
 
 
-@dataclass(slots=True)
+@dataclass
 class StaticTokenProvider:
     """Simple token provider that always returns the same token."""
 

src/foxnose_sdk/config.py

@@ -4,7 +4,7 @@
 from typing import Mapping, MutableMapping
 
 
-@dataclass(slots=True)
+@dataclass
 class RetryConfig:
     """
     Controls HTTP retry behavior for idempotent requests.
@@ -34,7 +34,7 @@ def as_dict(self) -> MutableMapping[str, object]:
 DEFAULT_USER_AGENT = "foxnose-sdk/0.1.0"
 
 
-@dataclass(slots=True)
+@dataclass
 class FoxnoseConfig:
     """
     General transport-level configuration shared by all clients.