`BulkOperation.path` is required in `BulkRequest`

[azmeuk]

RFC7644 indicates that BulkOperation.path is required in BulkRequest:

  path  The resource's relative path to the SCIM service provider's
     root.  If "method" is "POST", the value must specify a resource
     type endpoint, e.g., /Users or /Groups, whereas all other
     "method" values must specify the path to a specific resource,
     e.g., /Users/2819c223-7f76-453a-919d-413861904646.  REQUIRED in
     a request.

There should be a validator for this