How can I Add a File to an Activity in API v4?

Question

I create activities using the API, and now I need to add an uploaded file (meaning it was uploaded in a Drupal form) to the activity. I tried this:

$results = \Civi\Api4\Activity::create()
->addValue('activity_type_id', 91)
->addValue('target_contact_id', [ 8, ])
->addValue('source_contact_id', 2)
->addValue('subject', 'test')
->addChain('uploaded_invoice', 
  \Civi\Api4\File::create()->addValue('mime_type', 'text/plain')
     ->addValue('document', 'Just Testing')
     ->addValue('description', 'Invoice Scan')
)
->execute();

But this doesn't work, it creates the Activity, but no file is attached.

Answer 1

Unfortunately, as of this writing, there is no access to EntityFile in Api v4. This is the missing link between the Activity and File that you created. (In Api v3, you could add a file to an activity using Attachment.create, but that has not yet been ported to Api v4 either.)

I added a comment on this page, which tracks which entities are supported by Api v4.