Add support for authentication proxies (#321)

* add support for auth proxies

* Improve docs

siteroot/settings/base.py

@@ -182,3 +182,20 @@ MAX_ATTEMPTS = 5
 # specced systems like Raspberries. Should be OK as tasks are not time critical.
 BACKGROUND_TASK_RUN_ASYNC = True
 BACKGROUND_TASK_ASYNC_THREADS = 2
+
+# Enable authentication proxy support if configured
+LD_ENABLE_AUTH_PROXY = os.getenv('LD_ENABLE_AUTH_PROXY', False) in (True, 'True', '1')
+LD_AUTH_PROXY_USERNAME_HEADER = os.getenv('LD_AUTH_PROXY_USERNAME_HEADER', 'REMOTE_USER')
+LD_AUTH_PROXY_LOGOUT_URL = os.getenv('LD_AUTH_PROXY_LOGOUT_URL', None)
+
+if LD_ENABLE_AUTH_PROXY:
+    # Add middleware that automatically authenticates requests that have a known username
+    # in the LD_AUTH_PROXY_USERNAME_HEADER request header
+    MIDDLEWARE.append('bookmarks.middlewares.CustomRemoteUserMiddleware')
+    # Configure auth backend that does not require a password credential
+    AUTHENTICATION_BACKENDS = [
+        'django.contrib.auth.backends.RemoteUserBackend',
+    ]
+    # Configure logout URL
+    if LD_AUTH_PROXY_LOGOUT_URL:
+        LOGOUT_REDIRECT_URL = LD_AUTH_PROXY_LOGOUT_URL