feat: add selectedTenant to AccessKeyLoginOptions

[itamartal]

Summary

The AccessKeyLoginOptions in the Python SDK is missing the selectedTenant field, which is already supported by the Descope API and by other SDKs such as the Go SDK:

type AccessKeyLoginOptions struct {
	CustomClaims   map[string]any `json:"customClaims,omitempty"`
	SelectedTenant string         `json:"selectedTenant,omitempty"`
}

Without this field, users who need to exchange an access key with a specific tenant context (to get the dct claim set in the resulting JWT) must bypass the SDK and call the /v1/auth/accesskey/exchange REST API directly, manually constructing the request with the selectedTenant in loginOptions.

Changes

1. descope/common.py — Added selected_tenant parameter to AccessKeyLoginOptions, serialized as selectedTenant to match the API contract.

2. descope/auth.py — Updated exchange_access_key to filter out None values from the loginOptions dict, matching the Go SDK's omitempty behavior. This ensures selectedTenant is only included in the request when explicitly provided.

3. tests/test_auth.py — Added test case verifying that selected_tenant is correctly serialized as selectedTenant in the API request body.

Usage

from descope import AccessKeyLoginOptions

loc = AccessKeyLoginOptions(custom_claims={"k1": "v1"}, selected_tenant="my-tenant-id")
jwt_response = descope_client.exchange_access_key(access_key=key, login_options=loc)