This commit introduces a default value of `1` for the `PaymentType` property in the `Walk` entity. The `SqlDbContextModelSnapshot.cs` is updated to reflect this change, and the `SqlDbContext.cs` is configured to set the default value to `WalkPaymentType.MangoPay`. A new migration class `Walk_PaymentType_DefaultSet` is created to apply these changes to the database schema, ensuring that new records in the `Walks` table will have a default `PaymentType` of `1`.
