OpenApi: `discriminator.mapping` unsupported

[Jolanrensen]

While discriminator in combination with oneOf/allOf is supported for propertyName, it appears that mapping is absent.

https://swagger.io/docs/specification/data-models/inheritance-and-polymorphism/

It needs to be checked whether this is needed and can be supported.

Used in this example: https://youtrack.jetbrains.com/api/openapi.json

[Jolanrensen]

discriminator: propertyName points to the name variable of inheritors such that in code generation, inheritors of the current type can be told apart. The string content of that variable inside the inheritors needs to be exactly the name of the inheritor type. If this isn't the case, mapping can be used to map the propertyName to the correct reference, so that it's always visible which types inherit the current one.
For code generation in DF, propertyName and thus also mapping, can probably be ignored, since we simply take the name from the actual name of the object.