[cpprest] Dots and dashes are allowed in C++ identifiers.

Description

When generating cpprest dots and dashes are allowed for C++ identifier names which causes uncompilable code like:

class  Io.k8s.kubernetes.pkg.api.v1.Service
    : public ModelBase
{
...

Swagger-codegen version

2.4.0-SNAPSHOT from docker hub: https://hub.docker.com/r/swaggerapi/swagger-codegen-cli/

Swagger declaration file content or url

https://raw.githubusercontent.com/kubernetes/kubernetes/v1.10.4/api/openapi-spec/swagger.json

Command line used for generation

docker run swaggerapi/swagger-codegen-cli generate  --lang cpprest --output /output -i https://raw.githubusercontent.com/kubernetes/kubernetes/v1.10.4/api/openapi-spec/swagger.json

Steps to reproduce

run:

docker run swaggerapi/swagger-codegen-cli generate  --lang cpprest --output /output -i https://raw.githubusercontent.com/kubernetes/kubernetes/v1.10.4/api/openapi-spec/swagger.json

After generating any class in model directory will have such invalid names.

Suggest a fix/enhancement

Maybe map dots to "_", but care must be taken to avoid name clashes.

Start by running the documented Docker generation command against the Kubernetes Swagger declaration and inspect the generated files in the model directory. Trace how cpprest model class names are produced, then verify that dots and dashes no longer create invalid C++ identifiers and that the resulting names do not collide.