The messenger Send API gives me back the response (#546) The type of file you're trying to attach isn't allowed. Please try again with a different format. error code: 546, error_subcode: 154502
However, if I host the same exact image on Google Cloud instead of Amazon S3, then the image sends fine.
My link to the AWS image: https://s3.amazonaws.com/paloma-staging-public/files/conversation-step-56-80925.gif
My link to the google cloud image: https://storage.googleapis.com/callparty/thumbsup.gif
are there any special reasons that a link to an image stored on S3 would not work as an image attachment, but a link to an image stored on google cloud would work?
The answer was that for the AWS link the ContentType of the file was not set.
While uploading to S3 I had to manually set the ContentType of the file appropriately ("image/gif", "image/png" etc.) and for the google cloud storage this must have been automatically set.
This is why the S3 link causes an auto-download, and the google cloud link displays the image in the browser.
