Ambient-toolbox

* Added `url` parameter to `RequestProviderMixin`

* Added missing documentation about semantic database anonymisation
* Added missing documentation about string utils
* Added missing documentation about `get_namedtuple_choices()` helper
* Added missing documentation about `CrispyLayoutFormMixin`
* Added missing documentation about `ClassBasedViewTestMixin`

* Added missing documentation about email testing
* Updated Readme file

* Fixed `flit` configuration

* Setup `flit` for release management

* Added admin mixin `DeactivatableChangeViewAdminMixin`
* Added `response` parameter to testing middlewares