merge country and centre-id

[tomkralidis]

Fixes #562

Fixes #576

Note: we are keeping country in the MCF wis2box object, mostly as a means to help users pre-select their country to derive a related bounding box. If https://github.com/wmo-im/wis2box/blob/main/config-templates/countries.json is updated to be based on TLD (and not ISO 3166-3), then we can remove country entirely from the wis2box workflow (this can be part of another PR).

[tomkralidis]

TODO: update relevant screenshots (@maaikelimper)

[maaikelimper]

@tomkralidis Could we please add some clarification on choosing the correct center-id in the documentation here:

wis2box/docs/source/user/setup.rst

Lines 45 to 46 in 31e57b8

	The script will ask for 3-letter ISO country code for your wis2box. Please provide the 3-letter ISO country code for your country, for example ``FRA``.
	It will also ask for a centre-id. Please provide a string that identifies your organization and does not use spaces or special characters, for example ``meteofrance``.

Should the wis2box-create-config.py include a check that ensures the user provides a valid TLD prefix ?

[tomkralidis]

Note: we are keeping country in the MCF wis2box object, mostly as a means to help users pre-select their country to derive a related bounding box. If https://github.com/wmo-im/wis2box/blob/main/config-templates/countries.json is updated to be based on TLD (and not ISO 3166-3), then we can remove country entirely from the wis2box workflow (this can be part of another PR).

As for guidance on centre id selection, suggest we defer until the WIS2 Guide is approved.

Having said this, I've pushed a small doc update to help clarify in the meantime.

[maaikelimper]

Thanks for the clarification, approved.

I will prepare a separate PR to update wis2box-create-config.py and countries.json