Is map in query param supported?

In my use case my `GetSomethingRequest` includes a `map`, and I didn't manage to pass the map as a query param. So I have to attach a body to the `GET` request which is bad. This is how I define the messages and service:

```proto
message Key {
map data = 1;
string field = 2;
}
message GetSomethingRequest {
string parent = 1;
Key key = 2;
}
service SomeService {
rpc GetSomething(GetSomethingRequest) returns (Something) {
option (google.api.http) = {
get: "/v1/parent/{parent}/somethings"
};
}
}
```

I tried the following and neither of them works.

```
// also tried to replace [, ], {, }, :, = with percent encode.
// the first two are following https://github.com/grpc-ecosystem/grpc-gateway/pull/535
GET /v1/parent/parentname/somethings?field=aa&data[abc]=cba
GET /v1/parent/parentname/somethings?key.field=aa&key.data[abc]=cba
GET /v1/parent/parentname/somethings?key.field=aa&key.data={abc:cba}
```

So I wonder if map of primitives as query param is supported? If not any plans to add support for this? Thanks!