"Core XSD" containing definition of IRI for LD-compatible XMLs is weirdly linked and duplicated in output ZIP file

[jakubklimek]

This is not that urgent as we do not need this anyway (#688) but the "core XSD" is weirdly duplicated and linked when generating the ZIP file e.g. from this specification. See the output data structure, where the XSD is the 2022-07.xsd:

In addition, it is linked like this in the XSDs:

• ./2022-07.xsd in dokument-z-formuláře-pro-elektronické-podání
• ../place---detailed/2022-07.xsd in společné-specifikace-dokumentů/person-in-relationship-with-a-document
• ../place---detailed/2022-07.xsd in společné-specifikace-dokumentů/physical-person-as-a-person-with-relationship-to-a-document
• ./2022-07.xsd in společné-specifikace-dokumentů/place---detailed
• ../place---detailed/2022-07.xsd in společné-specifikace-dokumentů/place---simpler

So seemingly, one of the data structures is "first" and the rest link to it:

This core XML is published at https://schemas.dataspecer.com/xsd/core/2022-07.xsd, but that location may not be to the liking of every XSD author. Therefore I suggest:

1. Include this only once in the export and link to it correctly
2. Create XML-specific configuration options to
   1. Use the globally published version from the XSDs, i.e. <xs:import namespace="https://schemas.dataspecer.com/xsd/core/" schemaLocation="https://schemas.dataspecer.com/xsd/core/2022-07.xsd"/>
   2. If not, specify a custom "common" namespace, put it in the core XSD, and rely on the default mechanisms for correct paths or URLs.