VOD configs are now used to create VOD sessions. When you create a VOD session, specify a VOD config in the vodConfig field to use the config's sourceUri and adTagUri fields

## Change [VOD configs](https://cloud.google.com/video-stitcher/docs/how-to/managing-vod-configs) are now used to [create VOD sessions](https://cloud.google.com/video-stitcher/docs/how-to/creating-vod-sessions). When you create a VOD session, specify a VOD config in the [vodConfig](https://cloud.google.com/video-stitcher/docs/reference/rest/v1/projects.locations.vodSessions#VodSession.FIELDS.vod%5Fconfig) field to use the config's `sourceUri` and `adTagUri` fields.