Implement `endpoint` for `/v1/config`'s response

[kevinjqliu]

Feature Request / Improvement

/v1/config's response object (ConfigResponse) does not currently include the endpoints information.

iceberg-python/pyiceberg/catalog/rest/__init__.py

Lines 176 to 178 in c542e99

	class ConfigResponse(IcebergBaseModel):
	defaults: Properties | None = Field(default_factory=dict)
	overrides: Properties | None = Field(default_factory=dict)

Here's the corresponding spec definition: https://github.com/apache/iceberg/blob/59280a106ca5f378edfd47d3576c4d10011e5e80/open-api/rest-catalog-open-api.yaml#L2009-L2040

Let's add it so we can also use this information to check catalog capabilities