I have a problem that I don't know how to resolve.

I have two epics that do requests to api and update the store:

```
const mapSuccess = actionType => response => ({
  type: actionType + SUCCESS,
  payload: response.response,
});

const mapFailure = actionType => error => Observable.of({
  type: actionType + FAILURE,
  error,
});

const characterEpic = (action$, store) =>
  action$.ofType(GET_CHARACTER)
    .mergeMap(({ id }) => {
      return ajax(api.fetchCharacter(id))
        .map(mapSuccess(GET_CHARACTER))
        .catch(mapFailure(GET_CHARACTER));
    });

const planetsEpic = (action$, store) =>
  action$.ofType(GET_PLANET)
    .mergeMap(({ id }) => {
      return ajax(api.fetchPlanet(id))
        .map(mapSuccess(GET_PLANET))
        .catch(mapFailure(GET_PLANET));
    });

```

Now I have a simple scenario where I would like to create the third action that combines the two above, let's call it `fetchCharacterAndPlanetEpic`. How can I do it?
I think in many cases (and in my) it's important that result of the first action is dispatched to the store before the second begins. That would be probably trivial to do with Promises and `redux-thunk`, but I can't somehow think of a way to do it with `rxjs` and `redux-observable`.

Thanks!