I'm struggling to create an iframe manifest. I've read all the documentation and articles that I can find, but everything is fragmented. https://bitmovin.com/docs/player/articles/player-thumbnail-preview-support https://bitmovin.com/docs/encoding/api-reference/sections/manifests#/Encoding/PostEncodingManifestsHlsStreamsIframeByManifestIdAndStreamId 1. The process is unclear. Am I supposed to generate the thumbnails, then create a manifest with those thumbnails and attach it to the main manifest? Or does https://bitmovin.com/docs/encoding/api-reference/sections/manifests#/Encoding/PostEncodingManifestsHlsStreamsIframeByManifestIdAndStreamId do something completely different? I would love some help or direction on this.