Add HashtagFollow model and migration

users/migrations/0016_hashtagfollow.py

@@ -0,0 +1,49 @@
+# Generated by Django 4.1.7 on 2023-03-11 19:50
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("activities", "0012_in_reply_to_index"),
+        ("users", "0015_bookmark"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="HashtagFollow",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("created", models.DateTimeField(auto_now_add=True)),
+                (
+                    "hashtag",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="followers",
+                        to="activities.hashtag",
+                    ),
+                ),
+                (
+                    "identity",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="hashtag_follows",
+                        to="users.identity",
+                    ),
+                ),
+            ],
+            options={
+                "unique_together": {("identity", "hashtag")},
+            },
+        ),
+    ]

users/models/__init__.py

@@ -3,6 +3,7 @@ from .block import Block, BlockStates  # noqa
 from .bookmark import Bookmark  # noqa
 from .domain import Domain  # noqa
 from .follow import Follow, FollowStates  # noqa
+from .hashtag_follow import HashtagFollow  # noqa
 from .identity import Identity, IdentityStates  # noqa
 from .inbox_message import InboxMessage, InboxMessageStates  # noqa
 from .invite import Invite  # noqa

users/models/hashtag_follow.py

@@ -0,0 +1,22 @@
+from django.db import models
+
+
+class HashtagFollow(models.Model):
+    identity = models.ForeignKey(
+        "users.Identity",
+        on_delete=models.CASCADE,
+        related_name="hashtag_follows",
+    )
+    hashtag = models.ForeignKey(
+        "activities.Hashtag",
+        on_delete=models.CASCADE,
+        related_name="followers",
+    )
+
+    created = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        unique_together = [("identity", "hashtag")]
+
+    def __str__(self):
+        return f"#{self.id}: {self.identity} → {self.hashtag_id}"