Add tests for OAuth client and webhook notification handling

- Implement tests for `EbayOAuthClient` to verify authorization URL generation with configured scopes and token reuse logic.
- Add tests for `WebhookChallengeHandler` to ensure correct SHA256 response generation and for `WebhookSignatureParser` to validate extraction of known fields from signature strings.

ebay_client/generated/account/models/payment_policy_response.py

@@ -0,0 +1,158 @@
+from collections.abc import Mapping
+from typing import Any, TypeVar, Optional, BinaryIO, TextIO, TYPE_CHECKING, Generator
+
+from attrs import define as _attrs_define
+from attrs import field as _attrs_field
+
+from ..types import UNSET, Unset
+
+from ..types import UNSET, Unset
+from typing import cast
+from typing import Union
+
+if TYPE_CHECKING:
+  from ..models.payment_policy import PaymentPolicy
+
+
+
+
+
+T = TypeVar("T", bound="PaymentPolicyResponse")
+
+
+
+@_attrs_define
+class PaymentPolicyResponse:
+    """ The response payload for the <b>getPaymentPolicies</b> method. <br><br><span class="tablenote"><b>Note</b>:
+    Pagination has not yet been enabled for <b>getPaymentPolicies</b>, so all of the pagination-related fields are for
+    future use.</span>
+
+        Attributes:
+            href (Union[Unset, str]): This field is for future use.
+            limit (Union[Unset, int]): This field is for future use.
+            next_ (Union[Unset, str]): This field is for future use.
+            offset (Union[Unset, int]): This field is for future use.
+            payment_policies (Union[Unset, list['PaymentPolicy']]): A list of all of the seller's payment business policies
+                defined for the specified marketplace. This array will be returned as empty if no payment business policies are
+                defined for the specified marketplace.
+            prev (Union[Unset, str]): This field is for future use.
+            total (Union[Unset, int]): The total number of payment business policies retrieved in the result set.
+                <br><br>If no payment business policies are defined for the specified marketplace, this field is returned with a
+                value of <code>0</code>.
+     """
+
+    href: Union[Unset, str] = UNSET
+    limit: Union[Unset, int] = UNSET
+    next_: Union[Unset, str] = UNSET
+    offset: Union[Unset, int] = UNSET
+    payment_policies: Union[Unset, list['PaymentPolicy']] = UNSET
+    prev: Union[Unset, str] = UNSET
+    total: Union[Unset, int] = UNSET
+    additional_properties: dict[str, Any] = _attrs_field(init=False, factory=dict)
+
+
+
+
+
+    def to_dict(self) -> dict[str, Any]:
+        from ..models.payment_policy import PaymentPolicy
+        href = self.href
+
+        limit = self.limit
+
+        next_ = self.next_
+
+        offset = self.offset
+
+        payment_policies: Union[Unset, list[dict[str, Any]]] = UNSET
+        if not isinstance(self.payment_policies, Unset):
+            payment_policies = []
+            for payment_policies_item_data in self.payment_policies:
+                payment_policies_item = payment_policies_item_data.to_dict()
+                payment_policies.append(payment_policies_item)
+
+
+
+        prev = self.prev
+
+        total = self.total
+
+
+        field_dict: dict[str, Any] = {}
+        field_dict.update(self.additional_properties)
+        field_dict.update({
+        })
+        if href is not UNSET:
+            field_dict["href"] = href
+        if limit is not UNSET:
+            field_dict["limit"] = limit
+        if next_ is not UNSET:
+            field_dict["next"] = next_
+        if offset is not UNSET:
+            field_dict["offset"] = offset
+        if payment_policies is not UNSET:
+            field_dict["paymentPolicies"] = payment_policies
+        if prev is not UNSET:
+            field_dict["prev"] = prev
+        if total is not UNSET:
+            field_dict["total"] = total
+
+        return field_dict
+
+
+
+    @classmethod
+    def from_dict(cls: type[T], src_dict: Mapping[str, Any]) -> T:
+        from ..models.payment_policy import PaymentPolicy
+        d = dict(src_dict)
+        href = d.pop("href", UNSET)
+
+        limit = d.pop("limit", UNSET)
+
+        next_ = d.pop("next", UNSET)
+
+        offset = d.pop("offset", UNSET)
+
+        payment_policies = []
+        _payment_policies = d.pop("paymentPolicies", UNSET)
+        for payment_policies_item_data in (_payment_policies or []):
+            payment_policies_item = PaymentPolicy.from_dict(payment_policies_item_data)
+
+
+
+            payment_policies.append(payment_policies_item)
+
+
+        prev = d.pop("prev", UNSET)
+
+        total = d.pop("total", UNSET)
+
+        payment_policy_response = cls(
+            href=href,
+            limit=limit,
+            next_=next_,
+            offset=offset,
+            payment_policies=payment_policies,
+            prev=prev,
+            total=total,
+        )
+
+
+        payment_policy_response.additional_properties = d
+        return payment_policy_response
+
+    @property
+    def additional_keys(self) -> list[str]:
+        return list(self.additional_properties.keys())
+
+    def __getitem__(self, key: str) -> Any:
+        return self.additional_properties[key]
+
+    def __setitem__(self, key: str, value: Any) -> None:
+        self.additional_properties[key] = value
+
+    def __delitem__(self, key: str) -> None:
+        del self.additional_properties[key]
+
+    def __contains__(self, key: str) -> bool:
+        return key in self.additional_properties