$context variable isn't empty inside
wp_insert_attachment(), post meta info gets added with a meta key of
_wp_attachment_context. What is the intended purpose of
_wp_attachment_context? For example, can someone give some examples of the meta values I might store with this key?
After a little more research, I found out that WordPress stores values such as custom-header and custom-background against the meta key. I guess it's a way to distinguish them from the rest of the attachments in the system.