Adding sections with guide curves not working

[rainman110]

This applies for fuselages and wings.

TiGL should not crash or do unpredictable things when adding sections in a segment with existing guide curves. At the very least, TiGL should raise an error. --> Minimum requirement before merging to master.

If a section is created before or after a segment with guide curves, we could in theory add a dummy guide curve that connects to the guide curves of the segment.

Conceptually, guide curves are defined dependent of the sections. So a user should ideally create all sections first and then add guide curves.

[svengoldberg]

@joergbrech @merakulix @AntonReiswich We discussed this in the last session. IIRC, our idea was to throw an exception when sections are added in segments with gc. We also agreed on leaving it like this and see whether users are really seeking for this feature.
In this case we could think about implementing way adding those sections. Nevertheless, there are open questions on how exactly this should behave.

If you are fine with my suggested solution (so just throw an error and do not allow it; see 8f1c05a), I can open the PR.

[joergbrech]

A quick code-review on your commit here: Lets be specific in the error message that it is not supported out of principle, but it is not supported for now. We could even include the information i the error message that guide curves should be added once all sections are defined, which IMHO makes sense, because that's basically the data dependency in CPACS (guide curves reference existing sections, not vice versa). What do you think?

[svengoldberg]

Yes of course, that sounds reasonable.
The hint regarding the data dependency is also a good idea. I will add this

https://github.com/DLR-SC/tigl/commits/626_cpacs_creator_add_section_gc/