Zope.app.authentication

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- Nothing changed yet.

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- Drop support for Python 2.7, 3.3, 3.4, 3.5, 3.6.

- Add support for Python 3.7, 3.8, 3.9, 3.10, 3.11.

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- Drop test dependency on zope.app.zcmlfiles and zope.app.testing.

- Drop explicit dependency on ZODB3.

- Add support for Python 3.4, 3.5 and 3.6, and PyPy.

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* Move concrete IAuthenticatorPlugin implementations to
zope.pluggableauth.plugins. Leave backwards compatibility imports.

* Use zope.formlib throughout to lift the dependency on zope.app.form. As it
turns out, zope.app.form is still a indirect test dependency though.

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* Using python's ``doctest`` module instead of deprecated
``zope.testing.doctest[unit]``.

* Moved the following views from `zope.app.securitypolicy` here, to inverse
dependency between these two packages, as `zope.app.securitypolicy`
deprecated in ZTK 1.0:

- ``grant.html``
- ``AllRolePermissions.html``
- ``RolePermissions.html``
- ``RolesWithPermission.html``

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* Using the new `principalfactories.zcml` file, from ``zope.pluggableauth``,
to avoid duplication errors, in the adapters registration.