feat(nimbus): Add NimbusFeatureVersion model (#9812)

Because:

- we want to filter NimbusVersionedSchema based on its version; and
- having that information in the database makes it much easier to qeury

This commit:

- adds the NimbusFeatureVersion model.

Fixes #9811

experimenter/experimenter/experiments/migrations/0251_nimbusfeatureversion.py

@@ -0,0 +1,45 @@
+# Generated by Django 3.2.23 on 2023-11-22 18:02
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("experiments", "0250_nimbusexperiment_qa_status"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="NimbusFeatureVersion",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("major", models.IntegerField()),
+                ("minor", models.IntegerField()),
+                ("patch", models.IntegerField()),
+            ],
+            options={
+                "verbose_name": "Nimbus Feature Version",
+                "verbose_name_plural": "Nimbus Feature Versions",
+                "unique_together": {("major", "minor", "patch")},
+            },
+        ),
+        migrations.AlterField(
+            model_name="nimbusversionedschema",
+            name="version",
+            field=models.ForeignKey(
+                null=True,
+                on_delete=django.db.models.deletion.CASCADE,
+                to="experiments.nimbusfeatureversion",
+            ),
+        ),
+    ]

experimenter/experimenter/experiments/models.py

@@ -1245,13 +1245,30 @@ class NimbusFeatureConfig(models.Model):
         return self.name
 
 
+class NimbusFeatureVersion(models.Model):
+    major = models.IntegerField(null=False)
+    minor = models.IntegerField(null=False)
+    patch = models.IntegerField(null=False)
+
+    class Meta:
+        verbose_name = "Nimbus Feature Version"
+        verbose_name_plural = "Nimbus Feature Versions"
+        unique_together = ("major", "minor", "patch")
+
+    def __repr__(self):  # pragma: no cover
+        return f"<NimbusFeatureVersion({self.major}, {self.minor}, {self.patch})>"
+
+    def __str__(self):  # pragma: no cover
+        return f"{self.major}.{self.minor}.{self.patch}"
+
+
 class NimbusVersionedSchema(models.Model):
     feature_config = models.ForeignKey(
         NimbusFeatureConfig,
         related_name="schemas",
         on_delete=models.CASCADE,
     )
-    version = models.CharField(max_length=255, null=True)
+    version = models.ForeignKey(NimbusFeatureVersion, on_delete=models.CASCADE, null=True)
     schema = models.TextField(blank=True, null=True)
     sets_prefs = ArrayField(models.CharField(max_length=255, null=False, default=list))
 
@@ -1260,12 +1277,20 @@ class NimbusVersionedSchema(models.Model):
         verbose_name_plural = "Nimbus Versioned Schemas"
         unique_together = ("feature_config", "version")
 
-    def __str__(self):  # pragma: no cover
+    def __repr__(self):  # pragma: no cover
         return (
             f"<NimbusVersionedSchema(feature_config_id={self.feature_config_id}, "
-            f"version={self.version!r})>"
+            f"version={self.version})>"
         )
 
+    def __str__(self):  # pragma: no cover
+        as_str = f"NimbusVersionedSchema for {self.feature_config_id}"
+
+        if self.version is not None:
+            as_str = f"{as_str} at {self.version}"
+
+        return as_str
+
 
 class NimbusChangeLogManager(models.Manager["NimbusChangeLog"]):
     def latest_change(self):