Develop minimum um2nc for esm1.5 postprocessing

[truth-quark]

This is a high level/umbrella issue to group general work on the task of preparing a minimum um2nc for esm1.5 post-processing.

Background: multiple different versions of um2nc exist on gadi, with uncertain provenance. This project is based on Martin Dix's latest version (copied in 16/6/2024). Different copies had different module names, depending on which author build a customised version. In this repo um2nc is considered synonymous with um2netcdf.

General tasks include:

• [ ] Document functional requirements in issues
• [ ] Code cleanups for release
• [ ] Ensure script can execute
• [ ] Basic setup configuration
• [ ] Test driven repair
  • [ ] Build workflow/integration test
  • [ ] Refactor code with tests (ensure correct processing, improve structure of code)
• [ ] Test/restructure as many functional requirements as possible

[truth-quark]

This requirement also relates to this issue: https://github.com/ACCESS-NRI/access-esm1.5-configs/issues/3