refactor!: enhance avro mod typings (#146)

confluent_kafka-stubs/avro/cached_schema_registry_client.pyi

@@ -7,7 +7,7 @@ from __future__ import annotations
 # standard library
 from logging import Logger
 from pathlib import Path
-from typing import TYPE_CHECKING, DefaultDict, Literal
+from typing import TYPE_CHECKING, ClassVar, DefaultDict, Literal
 
 from .error import ClientError as ClientError
 from .load import loads as loads
@@ -28,11 +28,11 @@ ACCEPT_HDR: str
 log: Logger
 
 class CachedSchemaRegistryClient:
-    url: str | dict
-    subject_to_schema_ids: DefaultDict[str, dict]
-    id_to_schema: DefaultDict[str, dict]
-    subject_to_schema_versions: DefaultDict[str, dict]
-    auto_register_schemas: bool
+    url: ClassVar[str | dict]
+    subject_to_schema_ids: ClassVar[DefaultDict[str, dict]]
+    id_to_schema: ClassVar[DefaultDict[str, dict]]
+    subject_to_schema_versions: ClassVar[DefaultDict[str, dict]]
+    auto_register_schemas: ClassVar[bool]
 
     def __init__(
         self,

confluent_kafka-stubs/avro/error.pyi

@@ -10,8 +10,6 @@ from typing import ClassVar
 from ..cimpl import Message
 
 class ClientError(Exception):
-    """Error thrown by Schema Registry clients"""
-
     message: ClassVar[Message]
     http_code: ClassVar[int]
 

confluent_kafka-stubs/avro/serializer/message_serializer.pyi

@@ -7,7 +7,7 @@ from __future__ import annotations
 # standard library
 from io import BytesIO
 from logging import Logger
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any, Callable, ClassVar
 
 from ...schema_registry.schema_registry_client import SchemaRegistryClient
 from .. import ClientError as ClientError
@@ -33,11 +33,11 @@ class ContextStringIO(BytesIO):
     def __exit__(self, *args): ...
 
 class MessageSerializer:
-    registry_client: SchemaRegistryClient
-    id_to_decoder_func: dict[int, Callable]
-    id_to_writers: dict[int, bytes]
-    reader_key_schema: str | bytes | None = None
-    reader_value_schema: str | bytes | None = None
+    registry_client: ClassVar[SchemaRegistryClient]
+    id_to_decoder_func: ClassVar[dict[int, Callable]]
+    id_to_writers: ClassVar[dict[int, bytes]]
+    reader_key_schema: ClassVar[str | bytes | None]
+    reader_value_schema: ClassVar[str | bytes | None]
 
     def __init__(
         self,