* The `ItemDefinition` does not validate the bounds for `period` any longer. This has to be done by the integrating party. This is along the lines of what is alrady happening with `expiry`.
5.8.0
* The `is_permalink` option was added as a parameter when generating purchase URLs, which is available for contributions and donations. If present and `True`, this generates a non-expiring link.
* Adjusted "a year" to 365 days instead of 12 * 31 days.
5.7.0
* The `ITEM_TYPE_POLITICAL_CONTRIBUTION` constant was added to the `constants` module. It's to be used in conjuction with the `item_type` attribute on an `ItemDefinition`.
* The `ItemDefinition` gained a new key-word argument `election_id` that must be set when `item_type` is `ITEM_TYPE_POLITICAL_CONTRIBUTION` when creating purchase URLs for political contributions.
5.6.0
* The `ItemDefinition` gained a new key-word argument `item_type` that must be set to `'contribution'` or `'donation'` when creating purchase URLs for contributions or donations.
* Two new constants were added to the `constants` module: `ITEM_TYPE_CONTRIBUTION` and `ITEM_TYPE_DONATION` to be used in conjuction with the new `item_type` attribute on an `ItemDefinition`.
5.5.0
* Added support for Python 3.6
* Allowed `article_ids` when fetching access data to be a `collections.Iterable` and not just a string, list or tuple. Passing anything else will raise a `DeprecationWarning`.