Add support for blocking the changing of password for specify users.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/user_management/models.py

@@ -0,0 +1,24 @@
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import models
+from django.utils.translation import ugettext_lazy as _
+
+
+class UserOptions(models.Model):
+    user = models.OneToOneField(
+        on_delete=models.CASCADE, related_name='user_options',
+        to=settings.AUTH_USER_MODEL, unique=True, verbose_name=_('User')
+    )
+    block_password_change = models.BooleanField(
+        default=False,
+        verbose_name=_('Forbid this user from changing their password.')
+    )
+
+    class Meta:
+        verbose_name = _('User settings')
+        verbose_name_plural = _('Users settings')
+
+    def natural_key(self):
+        return self.user.natural_key()
+    natural_key.dependencies = [settings.AUTH_USER_MODEL]