feat(action): allow for 204 no content returns on resources

[joecrowley-synergy]

This enables the ability to test servers that return 204 when resources with hrefs aren't yet created, e.g. default der controls. This is highlighted as the preferred way to represent such situations as per IEEE2030.5:2018 section 5.5.2.5.

I have made it that when a None is returned from get_resource_for_step from within action_refresh_resource it deletes the resource. I'm making the leap here that when something exists and is nullified it is then removed from the resource tree. If that can even happen i'm not sure.

Have run S-ALL-49 on our server tests which now allows for this test to pass (it doesn't setup a DDERC on one of the DERPS which was causing discovery to raise an exception, attempting to parse a null body).

[joshvote]

No strong feelings as to the interpretation being valid or not - but we do need to make sure that if we "loosen" the requirements on the server side, that we tighten up the compliance on the client side.

We probably need the CIRG involved (or at least get a few more eyes on this).

[joecrowley-synergy]

Issue template submitted. Awaiting response.

[joecrowley-synergy]

ok further investigation into the written test procedures v1.2, table 11 has a set of default configurations. As part of those configurations it has stated default opModExpLimW, opModImpLimW and setGradW default der controls. I have now implemented this within my plugin as the default der control for the associated object. That will nullify the basis on which this ticket was raised, however it is still something that is being discussed.