models: Replace is_guest and is_realm_admin with UserProfile.role.

This new data model will be more extensible for future work on
features like a primary administrator.

zerver/migrations/0248_userprofile_role_start.py

@@ -0,0 +1,49 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.24 on 2019-10-03 22:27
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+from django.db.backends.postgresql_psycopg2.schema import DatabaseSchemaEditor
+from django.db.migrations.state import StateApps
+
+# The values at the time of this migration
+ROLE_REALM_ADMINISTRATOR = 200
+ROLE_MEMBER = 400
+ROLE_GUEST = 600
+
+def update_role(apps: StateApps, schema_editor: DatabaseSchemaEditor) -> None:
+    UserProfile = apps.get_model('zerver', 'UserProfile')
+    for user in UserProfile.objects.all():
+        if user.is_realm_admin:
+            user.role = ROLE_REALM_ADMINISTRATOR
+        elif user.is_guest:
+            user.role = ROLE_GUEST
+        else:
+            user.role = ROLE_MEMBER
+        user.save(update_fields=['role'])
+
+def reverse_code(apps: StateApps, schema_editor: DatabaseSchemaEditor) -> None:
+    UserProfile = apps.get_model('zerver', 'UserProfile')
+    for user in UserProfile.objects.all():
+        if user.role == ROLE_REALM_ADMINISTRATOR:
+            user.is_realm_admin = True
+            user.save(update_fields=['is_realm_admin'])
+        elif user.role == ROLE_GUEST:
+            user.is_guest = True
+            user.save(update_fields=['is_guest'])
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('zerver', '0247_realmauditlog_event_type_to_int'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='userprofile',
+            name='role',
+            field=models.PositiveSmallIntegerField(null=True),
+        ),
+
+        migrations.RunPython(update_role, reverse_code=reverse_code),
+    ]