Add disk usage statistics

- add model CustomerPackageDiskUsage for hosting package disk usage
  statistics
- add REST API endpoint for submittings statistics for disk, mysql and
  pgsql usage
- add disk usage information to hosting package detail view
- add separate hosting package disk usage statistic view

gnuviechadmin/hostingpackages/urls.py

@@ -4,7 +4,7 @@ This module defines the URL patterns for hosting package related views.
 """
 from __future__ import absolute_import
 
-from django.urls import re_path
+from django.urls import path, re_path
 
 from .views import (
     AddHostingOption,
@@ -12,7 +12,9 @@ from .views import (
     CreateCustomerHostingPackage,
     CreateHostingPackage,
     CustomerHostingPackageDetails,
+    CustomerHostingPackageDiskUsageDetails,
     HostingOptionChoices,
+    UploadCustomerPackageDiskUsage,
 )
 
 urlpatterns = [
@@ -42,4 +44,14 @@ urlpatterns = [
         AddHostingOption.as_view(),
         name="add_hosting_option",
     ),
+    path(
+        "<int:package>/disk-usage/",
+        CustomerHostingPackageDiskUsageDetails.as_view(),
+        name="disk_usage_details",
+    ),
+    path(
+        "upload-disk-usage/",
+        UploadCustomerPackageDiskUsage.as_view(),
+        name="upload_disk_usage",
+    ),
 ]