Content rest api documents collection resource shows all properties

With HSTTWO-3939 the option was added to specify some properties that will show up in the document collection. You can get the output of the title property for example by specifying

/api/documents?_attributes=myhippoproject:title

If you now omit this parameter, all properties are added to the output. This is not intended for the document collection output. Without the _attributes parameter no extra content properties should be shown. In case of the detail output, it works correctly: without the _attributes parameter all properties should be output.

It is not breaking backwards compatibility, but it can make the volume of the output much bigger, and thus result in slower performance.

Without the _attributes parameter available, there should be no extra content properties in the output.