Need to refine the APIs' parameters.

[zongzw]

If we define the API like this:

  @get(prefix + '/services', {
    responses: {
      '200': Schema.response(Service, 'Successfully retrieve Service resource'),
    },
  })
  async find(
    @param.query.object('filter', getFilterSchemaFor(Service)) filter?: Filter,
  ): Promise<CollectionResponse> {
    let data = await this.serviceRepository.find(filter, {
      tenantId: await this.tenantId,
    });
    return new CollectionResponse(Service, data);
  }

It may be hard for user to pass object-type query parameters, it should be refined.