Django-esteid

With this release we now allow `action.get_bdoc_container_file` to return a file-like object too. This is mostly a compatibility fix for users of legacy implementations as it is part of the deprecated api. As a result it is easier to use the actions api with remote filesystem backends like S3.

Also:

- Use Github actions instead of travis for CI
- Update smartid test identity codes in unit tests
- Add tests for `open_container` method
- Use poetry for packaging and dependency management

Note: As the packaging tooling was updated we will create some release candidates before publishing the final release in PyPI.

(Note: this tag doesn't change anything but version, compared to 3.1, so copying the 3.1 description here)

Added Authentication with ID card, Smart ID & Mobile ID.

Also:

* Added pylint.
* Fixed a problem with errors not being handled properly in the SessionViewMixin.
* Changed some EsteidError classes to inherit from InvalidParameters.
* Added deprecation warnings and pragma: no cover to old deprecated modules.

Added Authentication with ID card, Smart ID & Mobile ID.

Also:
* Added pylint.
* Fixed a problem with errors not being handled properly in the SessionViewMixin.
* Changed some EsteidError classes to inherit from InvalidParameters.
* Added deprecation warnings and pragma: no cover to old deprecated modules.

Due to shutdown of the DigidocService:
* Switched to the MobileID REST API;
* Using locally generated signatures for ID card;
* Removed digidoc service support;
* Introduced new signing API;
* Moved ASiC-E container support and certificates into separate libraries.

Implemented DDS-free ID card signing. Dropped support for Python < 3.6 and Django < 1.11. Updated libraries.

- Fix compatibility with `attrs>=19.2.0`