feat: add subscription and transaction repositories

- Implemented SubscriptionRepository with methods to get, create, and update subscriptions.
- Added BalanceTXRepository for creating and retrieving balance transactions.
- Introduced a test script for simulating Pally webhook for local testing.

db/models/transactions.py

@@ -0,0 +1,41 @@
+from datetime import datetime
+from enum import StrEnum
+from typing import TYPE_CHECKING
+
+from sqlalchemy import BIGINT, INTEGER, TEXT, DateTime, Enum, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from db.base import Base
+
+if TYPE_CHECKING:
+    from db.models.users import User
+
+
+class BalanceTxType(StrEnum):
+    DEPOSIT = "deposit"
+    PURCHASE = "purchase"
+    REFUND = "refund"
+    REFERRAL_BONUS = "referral"
+    MANUAL = "manual"
+
+
+class BalanceTransaction(Base):
+    __tablename__ = "balance_transactions"
+
+    id: Mapped[int] = mapped_column(BIGINT, autoincrement=True, primary_key=True)
+    user_id: Mapped[int] = mapped_column(BIGINT, ForeignKey("users.id"), nullable=False, index=True)
+    amount: Mapped[int] = mapped_column(INTEGER, nullable=False)
+
+    tx_type: Mapped[BalanceTxType] = mapped_column(
+        Enum(BalanceTxType, name="balancetxtype", values_callable=lambda x: [e.value for e in x]),
+        nullable=False,
+    )
+    balance_before: Mapped[int] = mapped_column(INTEGER, nullable=False)
+    balance_after: Mapped[int] = mapped_column(INTEGER, nullable=False)
+    description: Mapped[str] = mapped_column(TEXT, nullable=True)
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, default=lambda: datetime.now()  # noqa: PLW0108
+    )
+
+    user: Mapped["User"] = relationship("User", back_populates="balance_transactions")