docs(0074): add business partner script variants

[nicoprow]

Summary

Applies the script variants contribution to the CX-0074 Business Partner Gate API standard, standardising the scriptVariants attribute already present in the reference implementation.

• Adds Script Variants (List of Business Partner Script Variant) to the Business Partner entity in §1.5.2.1
• Adds new sub-section §1.5.2.1.2 BUSINESS PARTNER SCRIPT VARIANT defining the full data model: BusinessPartnerScriptVariant with nested LegalEntityScriptVariant, SiteScriptVariant, and AddressScriptVariant (each with a physical and, where applicable, alternative address variant)
• Specifies that available script codes are operator-defined and published via the Business Partner Data Pool (CX-0012), not validated at the Gate API level
• Clarifies that script variants flow through the enrichment process like any other business partner attribute, and that deduplication of identical script codes is the enrichment process's responsibility

Fields standardised in physical address script variant: postal code, city, district, street name/prefix/suffix fields, building, floor, door, company postal code, industrial zone. Fields present in the reference implementation but not meaningful to vary by script (taxJurisdictionCode, house number, milestone, direction) are intentionally excluded from the standard.

Diagrams

• Updated business-partner.puml / .svg: removes obsolete commented-out script variant draft and adds BusinessPartnerScriptVariant class with ScriptCode / NameParts and a composition relation from BusinessPartner
• New business-partner-script-variant.puml / .svg: dedicated diagram for §1.5.2.1.2 showing the full script variant hierarchy

Change Request

https://github.com/catenax-eV/product-standardization-prod/issues/667