Fix generated code in cases where multiple APIs define the same options.

[brendandburns]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\. If contributing template-only or documentation-only changes which will change sample output, be sure to build the project first.
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Description of the PR

Add the class name to the options struct in case APIs cough Kubernetes cough re-use the same options names in multiple different revisions of the API.

cc @antihax @bvwells @grokify @kemokemo

[wing328]

Looks like the CI tests failed with the following errors:

# _/home/circleci/OpenAPITools/openapi-generator/samples/client/petstore/go/go-petstore
go-petstore/api_fake.go:109:92: undefined: FakeOuterBooleanSerializeOpts
go-petstore/api_fake.go:207:94: undefined: FakeOuterCompositeSerializeOpts
go-petstore/api_fake.go:309:91: undefined: FakeOuterNumberSerializeOpts
go-petstore/api_fake.go:407:91: undefined: FakeOuterStringSerializeOpts
go-petstore/api_fake.go:752:167: undefined: TestEndpointParametersOpts
go-petstore/api_fake.go:896:85: undefined: TestEnumParametersOpts
go-petstore/api_fake.go:999:166: undefined: TestGroupParametersOpts
go-petstore/api_pet.go:109:88: undefined: DeletePetOpts
go-petstore/api_pet.go:530:96: undefined: UpdatePetWithFormOpts
go-petstore/api_pet.go:612:89: undefined: UploadFileOpts
go-petstore/api_pet.go:612:89: too many errors
FAIL	_/home/circleci/OpenAPITools/openapi-generator/samples/client/petstore/go [build failed]
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec (go-test) on project Goswagger: Command execution failed. Process exited with an error: 2 (Exit value: 2) -> [Help 1]

[wing328]

May I suggest adding an option in the Go client generator to make the change backward compatible?

[wing328]

@brendandburns I've filed #4564 to add an option to prefix the struct with the class name so closing this one.