[BUG] [swift5] Generated Swift oneOfs are not Hashable

Created by: denizdogan

The generated Swift structs are Hashable, but the oneOfs are not Hashable. This causes build errors when a Hashable struct contains non-Hashable oneOfs. Example failing Swift output:

public struct User: Codable, Hashable {
    public var gender: GenderOneOf?
}

public enum GenderOneOf: Codable { // <- missing Hashable
    // irrelevant
}

openapi-generator version

5.3.1-SNAPSHOT

Related issues/PRs

PR which added Hashable to structs:

https://github.com/OpenAPITools/openapi-generator/pull/9166

Suggest a fix

Just add Hashable to the oneOf templates.