SendToDeviceApi (client-server-api 0.9.0 API)

```
@Path("/_matrix/client/r0/sendToDevice")
@Consumes("application/json")
@Produces("application/json")
public interface SendToDeviceApi
```
This module provides a means by which clients can exchange signalling messages without them being stored permanently as part of a shared communication history. A message is delivered exactly once to each client device.
The primary motivation for this API is exchanging data that is meaningless or undesirable to persist in the room DAG - for example, one-time authentication tokens or key data. It is not intended for conversational data, which should be sent using the normal /rooms/<room_id>/send API for consistency throughout Matrix.

Method Summary

Modifier and Type	Method	Description
`void`	`send(String eventType, String txnId, SendToDeviceRequest sendToDeviceRequest, javax.ws.rs.core.UriInfo uriInfo, javax.ws.rs.core.HttpHeaders httpHeaders, javax.ws.rs.container.AsyncResponse asyncResponse, javax.ws.rs.core.SecurityContext securityContext)`	This endpoint is used to send send-to-device events to a set of client devices.

- Method Detail
  - send
```
@PUT
@Path("/{eventType}/{txnId}")
void send(@PathParam("eventType")
          String eventType,
          @PathParam("txnId")
          String txnId,
          SendToDeviceRequest sendToDeviceRequest,
          @Context
          javax.ws.rs.core.UriInfo uriInfo,
          @Context
          javax.ws.rs.core.HttpHeaders httpHeaders,
          @Suspended
          javax.ws.rs.container.AsyncResponse asyncResponse,
          @Context
          javax.ws.rs.core.SecurityContext securityContext)
```
    This endpoint is used to send send-to-device events to a set of client devices.
    Requires auth: Yes.
    Return: EmptyResponse.
    Status code 200: The message was successfully sent.
    
    Parameters:
    
    eventType - Required. The type of event to send.
    
    txnId - Required. The transaction ID for this event. Clients should generate an ID unique across requests with the same access token; it will be used by the server to ensure idempotency of requests.
    
    sendToDeviceRequest - Request body.
    
    uriInfo - Request Information.
    
    httpHeaders - Http headers.
    
    asyncResponse - Asynchronous response.
    
    securityContext - Security context.