docs: public com.squareup.okhttp.Call postCharactersCharacterIdMailAsync(Integer characterId, String datasource,
              String token, Mail mail, final ApiCallback<Integer> callback) throws ApiException {
  
          com.squareup.okhttp.Call call = postCharactersCharacterIdMailValidateBeforeCall(characterId, datasource, token,
                  mail, callback);
          Type localVarReturnType = new TypeToken<Integer>() {
          }.getType();
          apiClient.executeAsync(call, localVarReturnType, callback);
          return call;
      }