Add Seznam backend

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased](https://github.com/python-social-auth/social-docs/commits/master)
 
 ### Added
+- Added Seznam OAuth2 backend documentation.
 - Added Grafana OAuth2 backend documentation.
 - Added note on using extra auth arguments in Coinbase backend.
 - Added note on using tenants in Azure AD backend.

docs/backends/index.rst

@@ -141,6 +141,7 @@ Social backends
    reddit
    runkeeper
    salesforce
+   seznam
    shimmering
    shopify
    simplelogin

docs/backends/seznam.rst

@@ -0,0 +1,38 @@
+Seznam
+=========
+
+Seznam supports OAuth2 for developers to authenticate users for their apps.
+The documentation for the API can be found at `Seznam OAuth documentation`_.
+This backend also provides additional configuration options to support
+slightly different enterprise versions.
+
+1. Register a new application at `Application management`_, set the
+   ``redirect_uri`` to ``http://example.com/complete/seznam-oauth2/``,
+   replacing ``example.com`` with your domain.
+
+2. Fill ``client_id`` and ``client_secret`` values in the settings::
+
+    SOCIAL_AUTH_SEZNAM_OAUTH2_KEY = '<client_id>'
+    SOCIAL_AUTH_SEZNAM_OAUTH2_SECRET = '<client_secret>'
+
+- If you would like to access some additional information from the user,
+    you can set the ``SOCIAL_AUTH_SEZNAM_OAUTH2_SCOPE`` setting to a list
+    of extra scopes that are supported according to the `scope documentation`_.
+    For example, to request access to the user's phone number and avatar::
+    
+    SOCIAL_AUTH_SEZNAM_OAUTH2_SCOPE = ['contact-phone', 'avatar']
+
+User ID
+-------
+
+Seznam recommends the use of ``oauth_user_id`` as the user identifier instead
+of some immutable data as ``username`` or ``email`` because
+it can impose security risks if the user changes it.
+For that reason ``oauth_user_id`` is used by default, but for compatibility
+with the enterprise backed version, you can override this behavior by setting::
+
+    SOCIAL_AUTH_SEZNAM_OAUTH2_ID_KEY = 'id'
+
+.. _Seznam OAuth documentation: https://vyvojari.seznam.cz/oauth/doc?lang=en
+.. _Application management: https://vyvojari.seznam.cz/oauth/admin
+.. _scope documentation: https://vyvojari.seznam.cz/oauth/scopes?lang=en