[www-authenticate] Add stubs (#14688)

stubs/www-authenticate/METADATA.toml

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+version = "0.9.*"
+upstream_repository = "https://github.com/alexsdutton/www-authenticate"

stubs/www-authenticate/www_authenticate.pyi

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+from _typeshed import Incomplete
+from collections import OrderedDict
+from typing import Protocol, TypeVar, overload, type_check_only
+
+_T = TypeVar("_T")
+_VT = TypeVar("_VT")
+
+@type_check_only
+class _SupportsCasefold(Protocol):
+    def casefold(self) -> str: ...
+
+@type_check_only
+class _SupportsLower(Protocol):
+    def lower(self) -> str: ...
+
+class CaseFoldedOrderedDict(OrderedDict[str, _VT]):
+    def __getitem__(self, key: _SupportsCasefold | _SupportsLower) -> _VT: ...
+    def __setitem__(self, key: _SupportsCasefold | _SupportsLower, value: _VT) -> None: ...
+    def __contains__(self, key: _SupportsCasefold | _SupportsLower) -> bool: ...  # type: ignore[override]
+    # See overloads for dict class:
+    @overload
+    def get(self, key: _SupportsCasefold | _SupportsLower, default: None = None) -> _VT | None: ...
+    @overload
+    def get(self, key: _SupportsCasefold | _SupportsLower, default: _VT) -> _VT: ...
+    @overload
+    def get(self, key: _SupportsCasefold | _SupportsLower, default: _T) -> _VT | _T: ...
+    @overload  # type: ignore[override]
+    def pop(self, key: _SupportsCasefold | _SupportsLower, default: None = None) -> _VT | None: ...
+    @overload
+    def pop(self, key: _SupportsCasefold | _SupportsLower, default: _VT) -> _VT: ...
+    @overload
+    def pop(self, key: _SupportsCasefold | _SupportsLower, default: _T) -> _VT | _T: ...
+
+def parse(value: str) -> CaseFoldedOrderedDict[Incomplete]: ...