standardize packaging, tooling, docs, CI, and licensing

openapi_first/errors.pyi

@@ -1,6 +1,6 @@
-from typing import Optional
-
 class OpenAPIFirstError(Exception): ...
 
 class MissingOperationHandler(OpenAPIFirstError):
-    def __init__(self, *, path: str, method: str, operation_id: Optional[str] = ...) -> None: ...
+    def __init__(
+        self, *, path: str, method: str, operation_id: str | None = ...
+    ) -> None: ...