Fix: allow single CC/BCC recipient to be sent via form-data

[kevinkim-ogp]

Problem

Unable to send a single CC/BCC recipient when calling the transactional email API with form-data. This appears to be an edge case, as there are no issues when sending multiple CC/BCC recipients using form-data.

// how we normally append CC/BCC with more than 1 recipient
// this is accepted
formData.append('cc', '[email protected]')
formData.append('cc', '[email protected]')

// BUT fails when only 1 recipient, api validation interprets this as a string
// returning error message 'cc must be an array'
formData.append('cc', '[email protected]')


// other alternatives that were tested but not allowed by api
formData.append('cc[]', '[email protected]')
formData.append('cc', ['[email protected]'])  // form-data does not accept arrays
formData.append('cc', JSON.stringify(['[email protected]']))  // api does not accept stringified arrays

Note: Postman requires attachments to be sent via form-data

Related issue highlighted by another user: #2140

Solution

Enhance current CC/BCC validation to accept stringified arrays.
This change ensures:

• Compatibility with direct array submissions (existing implementation).
• Compatibility with form-data, where cc can be sent as a stringified JSON array.

[jia1]

Thanks @kevinkim-ogp!

I ran your branch on my local machine and specifying ["[email protected]"] works for me.

I'll take a look at the code right now.

[jia1]

Thank you, @kevinkim-ogp! Just need a bit of tidying up on your end and then this should be good to go.

[jia1]

LGTM, will let you know once we get this deployed