Briefly document in the Placement API reference: a) the use of Content-Type: application/json b) how to use microversion headers, including a link to the main Microversions reference. Change-Id: I60d7b9dfe4f1c50fc50eaf07a04848c220ffcf62
For more convinient text management each ROUTE_DECLARATIONS has its own inc file in api-ref. Change-Id: Ia2fd62ae7f401cad34ee7c2b355c9a5ab1c93f6b