HttpPushUri attribute in UpdateService schema

The expectation with POSTing an image to the URI specified by HttpPushUri is the update will being when the image is received. There are additional properties that have been added to help with scheduling aspects of it (similar to how you can use @redfish.OperationApplyTime to specify when the update starts when using the SimpleUpdate action). Version 1.4.0 of the UpdateService added "HttpPushUriOptions", which contains "HttpPushUriApplyTime/ApplyTime" and "HttpPushUriApplyTime/MaintenanceWindowStartTime".

I should note that due to how loose the definition is with HttpPushUri, most implementations likely treated this as an OEM method of updating. So, while in my mind those are the semantics around it, there's very little enforcement, and entirely possible an implementation requires another step to start the update.

We recently published a newer push method with the "MultipartHttpPushUri" property in version 1.6.0 of the UpdateService, which points to the Redfish spec for full details about expected behavior; this was added in 1.8.0 of the spec. Effectively you would POST to the URI specified by MultipartHttpPushUri using HTTP multipart forms, where one of the forms is a JSON body containing parameters (and annotations such as @redfish.OperationApplyTime if needed). Once the image is pushed, you'll get back a Task, and can monitor the progress of the update similar to how SimpleUpdate should behave.