Mint IGSN (soil DOIs) for our soil data

Some useful doco:
https://documentation.ands.org.au/display/DOC/IGSN+Service

Some other doco:
https://demo.ands.org.au/igsn/

API endpoint (non-prod):
https://demo.ands.org.au/igsn/api/igsn/30/mint

XSD: https://igsn.csiro.au/schemas/3.0/doc/

Potentially we can use: https://github.com/highsource/jsonix to work in the JSON world.
