Create Or Update Attachment

Adds an attachment to a piece of content. If the attachment already existsfor the content, then the attachment is updated (i.e. a new version of theattachment is created).Note, you must set a `X-Atlassian-Token: nocheck` header on the requestfor this method, otherwise it will be blocked. This protects against XSRFattacks, which is necessary as this method accepts multipart/form-data.The media type 'multipart/form-data' is defined in [RFC 7578](https://www.ietf....