Document "Enhanced Pricing"

[metas-Kay]

see: https://github.com/metasfresh/metasfresh/issues/3833

• IsPriceOverride checkbox
• PriceBase: Pricing System OR Fixed
• change "Discount Schema" to "Pricing Condition Schema"

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watch:

• https://github.com/metasfresh/metasfresh-webui-api/issues/940 (Hide Add New button in flat Discount Schema)
• https://github.com/metasfresh/metasfresh/issues/3835 (No recording of Products without pricing Conditions) & https://github.com/metasfresh/metasfresh-webui-frontend/issues/1603

[metas-Kay]

• Reorganize pricing section in documentation

[metas-Kay]

Add: Sales order: just-in-time creation of conditions for a product without conditions https://github.com/metasfresh/metasfresh/issues/3925

see also: https://github.com/metasfresh/metasfresh/issues/4016 (Pricing Conditions error when save)

and check: https://github.com/metasfresh/metasfresh/issues/3929 (Show BasePriceSystem in Document Line and Documents)