Add Splitwise clone backend

app/models.py

@@ -0,0 +1,67 @@
+from tortoise import Model, fields
+
+
+class User(Model):
+    id = fields.UUIDField(pk=True)
+    sub = fields.CharField(max_length=255, unique=True)
+    email = fields.CharField(max_length=255, null=True)
+    name = fields.CharField(max_length=255, null=True)
+    created_at = fields.DatetimeField(auto_now_add=True)
+
+    class Meta:
+        table = "users"
+
+
+class ExpenseReport(Model):
+    id = fields.UUIDField(pk=True)
+    title = fields.CharField(max_length=512)
+    creator: fields.ForeignKeyRelation["User"] = fields.ForeignKeyField(
+        "models.User", related_name="created_reports"
+    )
+    participants: fields.ReverseRelation["ExpenseParticipant"]
+    items: fields.ReverseRelation["ExpenseItem"]
+    created_at = fields.DatetimeField(auto_now_add=True)
+
+    class Meta:
+        table = "expense_reports"
+
+
+class ExpenseParticipant(Model):
+    id = fields.UUIDField(pk=True)
+    report: fields.ForeignKeyRelation["ExpenseReport"] = fields.ForeignKeyField(
+        "models.ExpenseReport", related_name="participants"
+    )
+    user: fields.ForeignKeyRelation["User"] = fields.ForeignKeyField(
+        "models.User", related_name="report_participations"
+    )
+
+    class Meta:
+        table = "expense_participants"
+        unique_together = (("report", "user"),)
+
+
+class ExpenseItem(Model):
+    id = fields.UUIDField(pk=True)
+    report: fields.ForeignKeyRelation["ExpenseReport"] = fields.ForeignKeyField(
+        "models.ExpenseReport", related_name="items"
+    )
+    description = fields.CharField(max_length=1024)
+    amount = fields.DecimalField(max_digits=12, decimal_places=2)
+    shares: fields.ReverseRelation["ExpenseShare"]
+
+    class Meta:
+        table = "expense_items"
+
+
+class ExpenseShare(Model):
+    id = fields.UUIDField(pk=True)
+    item: fields.ForeignKeyRelation["ExpenseItem"] = fields.ForeignKeyField(
+        "models.ExpenseItem", related_name="shares"
+    )
+    user: fields.ForeignKeyRelation["User"] = fields.ForeignKeyField(
+        "models.User", related_name="expense_shares"
+    )
+    percentage = fields.FloatField()
+
+    class Meta:
+        table = "expense_shares"