Okdata-sdk

* Use built-in JSON encoder from `requests` for `post`, `put` and `patch` methods.

* Handle error responses from status API update calls.

* Tweaked the webhook client to create and authorize tokens based on operations
(read, write) instead of tying them to a specific service.

* Add new SDK `WebhookClient` for managing webhook tokens with okdata-permission-api.

* Fix handling of Keycloak tokens that don't contain a refresh token.

* Added support for the new [permission API](https://github.com/oslokommune/okdata-permission-api).

* Retries have been re-enabled for low-level network errors (connection errors,
read errors, and redirects). The `retry` parameter now only controls the
maximum number of retries to perform on bad HTTP status codes.

* Fix refresh of Keycloak access token when refresh token is invalid, e.g.
due to inactive session because Keycloak server restarted.