Autoadmin: Incorporate the autoadmin app

Incorporate the external django-autoadmin app as a core app
and convert it into a Mayan app. This change adds the new
settings: "COMMON_AUTOADMIN_EMAIL", "AUTOADMIN_PASSWORD", and
"AUTOADMIN_USERNAME".

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/autoadmin/auth/allauth.py

@@ -0,0 +1,55 @@
+"""
+Authentication adapters for Allauth
+"""
+try:
+    from allauth.account.adapter import DefaultAccountAdapter
+except ImportError:
+    print('ERROR: This authentication adapter requires django-allauth.')
+    raise
+
+from django.conf import settings
+from django.contrib import messages
+from django.utils.translation import ugettext_lazy as _
+
+ADMIN_EMAIL_ADDRESSES = [email for name, email in settings.ADMINS]
+
+
+class AutoadminAccountAdapter(DefaultAccountAdapter):
+    """
+    Allauth account adapter that enables automatic grant of admin permissions
+    to users signing up having their email address listed in the ``ADMINS``
+    Django settings.  Django settings needed to activate this feature:
+
+        INSTALLED_APPS = [
+            'django.contrib.auth',
+            'django.contrib.sites',
+            'allauth',
+            'allauth.account',
+            'allauth.socialaccount',
+        ]
+
+        ACCOUNT_ADAPTER = 'autoadmin.auth.allauth.AutoadminAccountAdapter'
+
+    See also:
+    - http://django-allauth.readthedocs.io/en/latest/configuration.html
+    - http://django-allauth.readthedocs.io/en/latest/advanced.html#admin
+    """
+
+    def confirm_email(self, request, email_address):
+        """
+        Give superuser privileges automagically if the email address of a
+        user confirming their email is listed in ``settings.ADMINS``.
+        """
+        super(AutoadminAccountAdapter,
+              self).confirm_email(request, email_address)
+
+        if email_address.email in ADMIN_EMAIL_ADDRESSES:
+            user = email_address.user
+            user.is_staff = user.is_superuser = True
+            user.save()
+
+            messages.add_message(
+                request, messages.INFO,
+                _('Welcome Admin! You have been given superuser privileges. '
+                  'Use them with caution.')
+            )