feat(plugin-form-builder): Override payment fields

[mikecebul]

What?

Override the payment group field in form-submissions when using the form-builder-plugin.

Why?

I and probably others will enjoy using the form-builder-plugin features when using the payment field when creating forms, such as price conditions, redirects, emails, handle payment, ect. But may not need the specific fields pushed on to every form submission when using them.

How?

Before pushing the payment group field to a new form submission it checks if the original form uses the payment field. We also now check if there is a formSubmissionOverride field with the same name 'payments'. Instead of getting a duplicate field error it now bypasses adding the default payment fields.

This is my first PR

[mikecebul]

I see now that using the fields().some(field) is a pattern far removed from the usual merging from the function pattern Payload uses. I want to ensure the payment fields are always at the end of the submission so we need to push/append the fields. Since this is a plugin I thought it made sense to add a custom property custom.overridePaymentFields. I also added documentation. Anymore feedback will be greatly appreciated.

[mikecebul]

Ok, I worked really hard on this, learned a bunch, and I think I finally found a pattern that fits Payload. I switched to using a paymentFields(). I have it working in the tests and updated the docs as well explaining how the function can:

• Return false to disable payment fields entirely
• Return true to use the default payment fields (with a group field wrapper)
• Accept defaultPaymentFields (without the group field wrapper) as a parameter and return custom payment fields

In practice it can be used like this:

// payload.config.ts
formBuilder({
  // ...
  formSubmissionOverrides: {
    // ...
    paymentFields: ({ defaultPaymentFields }) => {
      return [
        {
          name: 'payment',
          type: 'group',
          fields: [
            ...defaultPaymentFields,
            {
              name: 'checkoutSession',
              type: 'text',
            },
          ],
        },
      ]
    },
  },
})