Error in pywa library for templates with image headers

[bcombes]

I'm not sure how best to file a bug report, but I found an error in the pywa send_template library when using image headers. According to the facebook docs, the key for the image location should be link and not url which results in the error below;

pywa.errors.WhatsAppError: WhatsAppError(message='(#100) Unexpected key "url" on param "template['components'][0]['parameters'][0]['image']".', details=None, code=100)

I've been trying to submit a PR to fix this, but not sure how.

[david-lev]

Issue opened #15