Query relations

[ps73]

It would be nice if we cannot just load relations via $eager but also query the related items with default feathers query and filter options.

Could look like this:

app.service('users').find({
  query: {
    $eager: {
      todos: ['title'],
    },
  },
});

Also it should be supported to filter for relations:

app.service('users').find({
  query: {
    todos: {
      tag1: {
        $in: ['TEST'],
      },
    },
  },
});

[ps73]

Selecting fields in $eager is possible since 0.4.0.

The filter example is not as easy to implement as I thought. Will close this issue because filtering is also possible with the new $rawWhere query param which is availabel since 0.5.0.