Invalid 'backend' attribute

[abelsromero]

There are methods to set backend as an attribute in AttributesBuilder and Attributes.

Unless I missed something this seems to be some mistake and should be deleted. Does anyone know of an actual use for that?

[robertpanzer]

I added this because Asciidoctor itself also stores this as an attribute:
https://github.com/asciidoctor/asciidoctor/blob/182b43ee445fdbb901941effe90e4e2247487489/lib/asciidoctor/cli/options.rb#L53
Since asciidoctorj-cli also has to pass it in an attribute to Asciidoctor, I'd personally say that it is ok to have it in Attributes.

[abelsromero]

OK, I am not going to deny it's weird but I see it's referred to in the official docs also https://docs.asciidoctor.org/asciidoc/latest/attributes/document-attributes-ref/#intrinsic-attributes.