[REQ][haskell-http-client] Support type-mapping and import-mappings

[guoshimin]

Is your feature request related to a problem? Please describe.

Describe the solution you'd like

Support type-mapping and import-mappings so we can provide custom implementation for selected model, for example, as is done in https://github.com/kubernetes-client/gen/blob/master/openapi/java.xml.

Describe alternatives you've considered

Additional context

In the OpenAPI spec for Kubernetes, there is an IntOrString type that's currently mapped to object if there is no custom mapping for it: https://github.com/kubernetes-client/gen/blob/c07ee54dcb0ae70c6ef587dded93b6ea75f354ea/openapi/preprocess_spec.py#L275. It would be more type safe to create (by hand) a Sum type for it.

@jonschoning

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[jonschoning]

type-mappings:

• openapi-generator changed it's behavior such that type-mappings cannot override the case that the spec defines a "primitive alias" for the type according to migrate from swagger-codegen to openapi-generator kubernetes-client/gen#93 (comment).
• We can supply a custom IntOrString with the existing generator, but we'll need to remove the intstr.IntOrString model definition from the spec.

import-mappings:

• i will look into adding support

[jonschoning]

modify preprocessor to remove models:
jonschoning/kubernetes-client-gen@b876d77

regen with import-mappings and type-mappings:
jonschoning/kubernetes-client-haskell@063587b

add CustomTypes and CustomInstances:
jonschoning/kubernetes-client-haskell@a268948

tests passed:
https://gist.github.com/jonschoning/df46961e0c999902eec07a3f7785822e

[guoshimin]

Thanks for the quick fix! I also did the same test and it worked.