Updated successful payment callback

inserting_transaction_in_db.py

def successful_payment_callback(update: Update, context):
    col = get_collection()
    receipt = update.message.successful_payment
    col.insert_one({"telegram_uid": update.message.chat.username, 
                   "donated_amount": receipt.total_amount,
                   "currency": receipt.currency,
                   "datetime": str(datetime.datetime.now())})
    print_col(col)
    update.message.reply_text("Thank you for your purchase!")