API Create conversation with attachments

Hello

I am trying to create a conversation with an attachment via API Create conversation (frontapp.com)

Currently, I am receiving new messages but without attachments.

My code looks like this:

$headers=@{}

$headers.Add("Accept", "application/json")

$headers.Add("Content-Type", "application/json")

$headers.Add("Authorization", "Bearer [my code]")

$response = Invoke-WebRequest -Uri 'https://api2.frontapp.com/channels/cha_XXX/messages' -Method POST -Headers $headers -ContentType 'application/json' -Body '{"to":["securitydesk@example.com"],"options":{"archive":false},"attachments":["data:text/plain;name=test.txt;base64,aBcDeF=="],"body":"test"}'