////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock API_EDGE_READ_HEAD
/// @brief reads a single edge head
///
/// @RESTHEADER{HEAD /_api/edge/{document-handle}, Read edge header}
///
/// @RESTURLPARAMETERS
///
/// @RESTURLPARAM{document-handle,string,required}
/// The handle of the edge document.
///
/// @RESTQUERYPARAMETERS
///
/// @RESTQUERYPARAM{rev,string,optional}
/// You can conditionally fetch an edge document based on a target revision id by
/// using the *rev* query parameter.
///
/// @RESTHEADERPARAMETERS
///
/// @RESTHEADERPARAM{If-None-Match,string,optional}
/// If the "If-None-Match" header is given, then it must contain exactly one
/// etag. If the current document revision is different to the specified etag,
/// an *HTTP 200* response is returned. If the current document revision is
/// identical to the specified etag, then an *HTTP 304* is returned.
///
/// @RESTHEADERPARAM{If-Match,string,optional}
/// You can conditionally fetch an edge document based on a target revision id by
/// using the *if-match* HTTP header.
///
/// @RESTDESCRIPTION
/// Like *GET*, but only returns the header fields and not the body. You
/// can use this call to get the current revision of an edge document or check if
/// it was deleted.
///
/// @RESTRETURNCODES
///
/// @RESTRETURNCODE{200}
/// is returned if the edge document was found
///
/// @RESTRETURNCODE{304}
/// is returned if the "If-None-Match" header is given and the edge document has
/// same version
///
/// @RESTRETURNCODE{404}
/// is returned if the edge document or collection was not found
///
/// @RESTRETURNCODE{412}
/// is returned if a "If-Match" header or *rev* is given and the found
/// document has a different version. The response will also contain the found
/// document's current revision in the *etag* header.
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////