code: @GET
      @Produces(MediaType.APPLICATION_JSON)
      @Description("Returns namespaces owned by user.")
      public List<NamespaceDto> getNamespacesByOwner(@Context HttpServletRequest req) {
          PrincipalUser remoteUser = validateAndGetOwner(req, null);
          List<Namespace> namespaces = _namespaceService.findNamespacesByOwner(remoteUser);
  
          return NamespaceDto.transformToDto(namespaces);
      }
docs: Returns namespaces owned by the user.
  
  @param   req  The HTTP request.
  
  @return  The namespaces owned by the user.