Pas.plugins.oidc

New features:

- Implement [plone/meta](https://github.com/plone/meta) and convert documentation to Markdown [ericof] [#32](https://github.com/collective/pas.plugins.oidc/issues/32)
- Drop support to Python 2.7 and Plone 5.2 [ericof] [33](https://github.com/collective/pas.plugins.oidc/issues/33)
- Implement restapi services to handle authentication flow [ericof] [38](https://github.com/collective/pas.plugins.oidc/issues/38)


Internal:

- Rewrite tests from unittest to pytest with [pytest-plone](https://pypi.org/project/pytest-plone/) [ericof] [#34](https://github.com/collective/pas.plugins.oidc/issues/34)
- Allow dict instances to hold userinfo [erral] [35](https://github.com/collective/pas.plugins.oidc/issues/35)
- Declare the minimum requirements for Plone/python in the readme [mamico] [36](https://github.com/collective/pas.plugins.oidc/issues/36)

- Allow dict instances to hold userinfo [erral]

- Added Spanish translation [macagua]

- Added improvements about i18n support [macagua]

- Drop python 2.7 and Plone 4 support [erral]

- Add support for the post_logout parameter for logout api. [ramiroluz]

- Catch exceptions during the OAuth process [erral]

- Update the plugin to make challenges.
An anonymous user who visits a page for which you have to be authenticated,
is redirected to the new require_login view on the plugin.
This works the same way as the standard require_login page of Plone.
[maurits]

- Add a property for the default userinfo instead of using only sub. [eikichi18]

- Call getProperty only once when getting redirect_uris or scope. [maurits]

- use getProperty accessor [mamico]

- Removed the hardcoded auth cookie name [alecghica]

- Fixed Python compatibility with version >= 3.6 [alecghica]

- check if url is in portal before redirect 2 [erral]

- manage came_from [mamico]