feat(payments): add paynow payment method

[KenLSM]

Problem

Admins want to only support certain forms to only provide payment through paynow (and disallowing other payment methods).

Closes FRM-1515

Solution

Added a payment_methods: string[] that can contain allowed payment methods

• Currently, only Paynow: 'Paynow' is supported

Backwards compatibility is supported through marking the new field as optional, and populated with [] when form.payments_channel is updated (during remove or add payment channel)

Breaking Changes

• No - this PR is backwards compatible

Features:

• Supports Paynow only through backend configuration by adding form.payments_channel.payment_methods: ["Paynow"]

Before & After Screenshots

BEFORE:

AFTER:

Tests

Regression

• Find an existing payment form
• Make a payment
• Ensure that both payment methods "Cards", and "Paynow" are available to be selected

New features

Newly created forms should have both "Cards" and "Paynow" payment methods

• Create a new payment form
• Make a payment
• Ensure that both payment methods "Cards", and "Paynow" are available to be selected

Forms with enabled toggle should only allow "Paynow" payment method

• Create a new payment form
• Upsert form.payments_channel.payment_methods: ["Paynow"] to the form on DB

  "payments_channel": {
    "channel": "Stripe",
    "target_account_id": "acct_****",
    "publishable_key": "pk_test_****",
    "payment_methods": [
      "Paynow"
    ]
  },

• Make a payment
• Ensure that only payment method "Paynow" is available to be selected

[linear]

FRM-1515 Backend restrict payment method to PayNow only

Description

Problem

Agencies do not want to offer cards as cards have higher fees, longer payout time and are subject to disputes.

Solution

Disable cards from backend when agencies request

We are not expecting multiple forms to have this toggled on, thus, db update will be sufficient.

[wanlingt]

lgtm! just one comment about Unset, I don't know what it's for