DefaultGenerator ignores return value of postProcessOperations and postProcessOperationsWithModels

Description

The postProcessOperations and postProcessOperationWithModels in the CodegenConfig are called by the DefaultGenerator (line 930 and 931 of DefaultGenerator.java swagger-codegen-3.0.4). We can work around it by changing the input map but this is not desirable.

There is also a problem with the following method in DefaultGenerator:

private void generateModels(List<File> files, List<Object> allModels) {
...
}

This method possible changes the allModels via the post processed model methods in the config classes. This method must be changed to return the (possibly) mutated models so that the subsequent generateApis method can consume it in the postProcessedOperationsWithModels method.

Swagger-codegen version

3.0.4 - not a regression just a programming error

Swagger declaration file content or url

Not a bug - code problem

Command line used for generation

Steps to reproduce

Related issues/PRs

Suggest a fix/enhancement

1. Change the two lines to add local variables to these methods:

Map<String, Object> postProcessedOperations = config.postProcessOperations(operations);
postProcessedOperations = config.postProcessOperationsWithModels(postProcessedOperations, allModels);

1. Change the private method generateModels to

private Map<String, Object> generateModels(List<File> files, List<Object> allModels) {
...
}

Start in DefaultGenerator.java around lines 930-931 and inspect how CodegenConfig.postProcessOperations and postProcessOperationsWithModels are called. Trace generateModels and generateApis to confirm how the possibly mutated models flow between them. Done means the returned post-processed maps and models are consumed by subsequent generation steps, with relevant existing tests or generation checks passing.