[FEATURE] Use environment variables in openapitools.json file

[gonzalad]

Could we provide a way to use environment variables in the openapitools.json file ?

This would provide an easy way to pass credentials when using a corporate repository for instance.

i.e.

{
    "generator-cli": {
        "repository": {
            "queryUrl": "https://${username}:${password}@artifactory.mycorp.com/maven-central/select?q=g:${group.id}+AND+a:${artifact.id}&core=gav&start=0&rows=200",
            "downloadUrl": "https://${username}:${password}@artifactory.mycorp.com/maven-central/${groupId}/${artifactId}/${versionName}/${artifactId}-${versionName}.jar"
        }
    }
}

Related issue:

• [Feature Request] Add authentication options for the repository configuration of the openapitools.json #552
• Make it easy to use with a private maven repository #835