code: @Path("/{dsID}")
      @POST
      public Response addDatastream(@PathParam(RestParam.PID) String pid,
                                    @PathParam(RestParam.DSID) String dsID,
                                    @QueryParam(RestParam.CONTROL_GROUP) @DefaultValue("X") String controlGroup,
                                    @QueryParam(RestParam.DS_LOCATION) String dsLocation,
                                    @QueryParam(RestParam.ALT_IDS) List<String> altIDs,
                                    @QueryParam(RestParam.DS_LABEL) String dsLabel,
                                    @QueryParam(RestParam.VERSIONABLE) @DefaultValue("true") Boolean versionable,
                                    @QueryParam(RestParam.DS_STATE) @DefaultValue("A") String dsState,
                                    @QueryParam(RestParam.FORMAT_URI) String formatURI,
                                    @QueryParam(RestParam.CHECKSUM_TYPE) String checksumType,
                                    @QueryParam(RestParam.CHECKSUM) String checksum,
                                    @QueryParam(RestParam.MIME_TYPE) String mimeType,
                                    @QueryParam(RestParam.LOG_MESSAGE) String logMessage,
                                    @QueryParam(RestParam.FLASH) @DefaultValue("false") boolean flash) {
          return addOrUpdateDatastream(true,
                                       pid,
                                       dsID,
                                       m_headers.getMediaType(),
                                       mimeType,
                                       controlGroup,
                                       dsLocation,
                                       altIDs,
                                       dsLabel,
                                       versionable,
                                       dsState,
                                       formatURI,
                                       checksumType,
                                       checksum,
                                       logMessage,
                                       false,
                                       null,
                                       flash);
      }
docs: <p>Add or modify a datastream.
  </p><p>
  POST /objects/{pid}/datastreams/{dsID} ? controlGroup dsLocation altIDs
  dsLabel versionable dsState formatURI checksumType checksum logMessage
  </p><p>
  Successful Response: Status: 201 Created Location: Datastream profile URL
  Content-Type: text/xml Body: XML datastream profile
  </p>