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/migrations/0007_add_disk_usage_table.py

@@ -0,0 +1,79 @@
+# Generated by Django 4.2.3 on 2023-07-22 17:31
+
+import django.utils.timezone
+import model_utils.fields
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    replaces = [
+        ("hostingpackages", "0007_add_disk_usage_table"),
+        ("hostingpackages", "0008_add_default_for_used_kb_change_uniqueness"),
+    ]
+
+    dependencies = [
+        ("hostingpackages", "0006_auto_20150125_1510"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="CustomerPackageDiskUsage",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                (
+                    "created",
+                    model_utils.fields.AutoCreatedField(
+                        default=django.utils.timezone.now,
+                        editable=False,
+                        verbose_name="created",
+                    ),
+                ),
+                (
+                    "modified",
+                    model_utils.fields.AutoLastModifiedField(
+                        default=django.utils.timezone.now,
+                        editable=False,
+                        verbose_name="modified",
+                    ),
+                ),
+                (
+                    "source",
+                    models.CharField(
+                        choices=[
+                            ("disk", "disk"),
+                            ("mysql", "mysql"),
+                            ("pgsql", "pgsql"),
+                        ],
+                        verbose_name="data source",
+                    ),
+                ),
+                ("item", models.CharField(verbose_name="data item")),
+                (
+                    "used_kb",
+                    models.PositiveBigIntegerField(
+                        default=0, verbose_name="space used in KiB"
+                    ),
+                ),
+                (
+                    "package",
+                    models.ForeignKey(
+                        help_text="The hosting package",
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="hostingpackages.customerhostingpackage",
+                        verbose_name="hosting package",
+                    ),
+                ),
+            ],
+            options={
+                "unique_together": {("package", "source", "item")},
+            },
+        ),
+    ]