fix: expose CustomDomainHeader in __all__ and fix return type annotation (#862)

## Changes:
- add `"CustomDomainHeader"` to `__all__`
- change `CustomDomainHeader` return type annotation from `Dict[str,
Any]` to `RequestOptions`

Closes #861

Author: rmad17

src/auth0/management/__init__.py

@@ -6667,6 +6667,7 @@ def __dir__():
     "CspReportingEndpoints",
     "CspReportingInfrastructure",
     "CustomDomain",
+    "CustomDomainHeader",
     "CustomDomainCustomClientIpHeader",
     "CustomDomainCustomClientIpHeaderEnum",
     "CustomDomainProvisioningTypeEnum",

src/auth0/management/management_client.py

@@ -5,6 +5,8 @@
 from json import dumps
 from typing import TYPE_CHECKING, Any, Callable, Dict, List, Optional, Union
 
+from .core.request_options import RequestOptions
+
 import httpx
 from .client import AsyncAuth0, Auth0
 from .token_provider import TokenProvider
@@ -36,7 +38,7 @@ def _enforce_custom_domain_whitelist(request: httpx.Request) -> None:
         del request.headers[CUSTOM_DOMAIN_HEADER]
 
 
-def CustomDomainHeader(domain: str) -> Dict[str, Any]:
+def CustomDomainHeader(domain: str) -> RequestOptions:
     """Create request options that set the Auth0-Custom-Domain header for a single request.
 
     When both a global custom_domain (set at client init) and a per-request