Making specutils compatible with data sets from fields besides astronomy

I'd like to raise a rather broad issue for discussion about making specutils compatible with spectroscopic data sets from fields such as laboratory plasma physics and heliophysics.

I'm coming from [PlasmaPy](http://docs.plasmapy.org/en/stable/), which is a young package that is striving to do for plasma physics what Astropy is doing for astronomy. Laboratory plasma experiments often have spectroscopic diagnostics. It would be wonderful to be able to use the same code to analyze remote observations, output from laboratory plasma diagnostics, and synthetic spectra from numerical simulations. ~~I'm also hoping to reduce unnecessary duplication of functionality since we have begun a separate package called [SpectroscoPyx](https://github.com/PlasmaPy/SpectroscoPyx/tree/master/spectroscopyx).~~ (edit: SpectroscoPyx is no longer under development) We've also had related discussions within the [Python in Heliophysics Community](http://heliopython.org/) too.

There are a couple of challenges that I can think of. It's pretty uncommon for laboratory plasma experiments to make experimental data openly available. I also don't know of any open metadata schemas for spectra.

I don't do much spectroscopy myself so I don't have use cases yet, though I've been intending to collect some from the plasma community. Probably the most common data formats are NetCDF and HDF5 (though the tokamak community uses [MDSplus](http://www.mdsplus.org/index.php/Introduction)). I'm wondering if creating a standard way of representing general spectra in HDF5 files and making them able to be read in using specutils would be enough.

This issue came about from an unconference session in Python in Astronomy 2019, at the suggestion of @nmearl. I'm curious about other people's thoughts on this. My sincere thanks to everyone who has contributed to this project!

Start by reviewing the six comments and the issue's proposed use cases for laboratory plasma, heliophysics, and synthetic spectra. Compare the stated NetCDF, HDF5, and MDSplus considerations, then establish concrete requirements and acceptance criteria before identifying an implementation entry point; the issue currently does not define what done looks like.

Written by the indexing model from the issue text.