Add installments. (fixes srmklive#602)

Some webhook verification fails with $request->all();

You can test "PAYMENT.SALE.COMPLETED"

`request->all {"id":"WH-0UX959158W078642N-2MW5123584490731L","event_version":"1.0","create_time":"2023-12-22T21:32:24.574Z","resource_type":"sale","event_type":"PAYMENT.SALE.COMPLETED","summary":"Payment completed for $ 3.67 USD","resource":{"amount":{"total":"3.67","currency":"USD","details":{"subtotal":"3.67"}},"payment_mode":"INSTANT_TRANSFER","create_time":"2023-12-22T21:32:18Z","custom":"id=3QWVF5ZswM&user=1&plan=2&interval=monthly&renew=10.4895&amount=3.671325&currency=USD&taxes=3%2C1&coupon=1","transaction_fee":{"currency":"USD","value":"0.62"},"billing_agreement_id":"I-MKX0RAHUCACW","update_time":"2023-12-22T21:32:18Z","protection_eligibility_type":"ITEM_NOT_RECEIVED_ELIGIBLE,UNAUTHORIZED_PAYMENT_ELIGIBLE","protection_eligibility":"ELIGIBLE","links":[{"method":"GET","rel":"self","href":"https://api.sandbox.paypal.com/v1/payments/sale/1SK68449YM493670F"},{"method":"POST","rel":"refund","href":"https://api.sandbox.paypal.com/v1/payments/sale/1SK68449YM493670F/refund"}],"id":"1SK68449YM493670F","state":"completed","invoice_number":null},"links":[{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-0UX959158W078642N-2MW5123584490731L","rel":"self","method":"GET"},{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-0UX959158W078642N-2MW5123584490731L/resend","rel":"resend","method":"POST"}]}
payload {"stdClass":{"id":"WH-0UX959158W078642N-2MW5123584490731L","event_version":"1.0","create_time":"2023-12-22T21:32:24.574Z","resource_type":"sale","event_type":"PAYMENT.SALE.COMPLETED","summary":"Payment completed for $ 3.67 USD","resource":{"amount":{"total":"3.67","currency":"USD","details":{"subtotal":"3.67"}},"payment_mode":"INSTANT_TRANSFER","create_time":"2023-12-22T21:32:18Z","custom":"id=3QWVF5ZswM&user=1&plan=2&interval=monthly&renew=10.4895&amount=3.671325&currency=USD&taxes=3%2C1&coupon=1","transaction_fee":{"currency":"USD","value":"0.62"},"billing_agreement_id":"I-MKX0RAHUCACW","update_time":"2023-12-22T21:32:18Z","protection_eligibility_type":"ITEM_NOT_RECEIVED_ELIGIBLE,UNAUTHORIZED_PAYMENT_ELIGIBLE","protection_eligibility":"ELIGIBLE","links":[{"method":"GET","rel":"self","href":"https://api.sandbox.paypal.com/v1/payments/sale/1SK68449YM493670F"},{"method":"POST","rel":"refund","href":"https://api.sandbox.paypal.com/v1/payments/sale/1SK68449YM493670F/refund"}],"id":"1SK68449YM493670F","state":"completed","invoice_number":""},"links":[{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-0UX959158W078642N-2MW5123584490731L","rel":"self","method":"GET"},{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-0UX959158W078642N-2MW5123584490731L/resend","rel":"resend","method":"POST"}]}}
`

Variable assignment fixed.