Support custom client package names

[emann]

Is your feature request related to a problem? Please describe.
Currently the name of the generated project is simply

self.project_name: str = f"{openapi.title.replace(' ', '-').lower()}-client"

with the generated module bearing the same name but with - replaced with _. It would be nice to be able to specify a custom name for the project, which would then propagate to the naming of the package.

Describe the solution you'd like
Add a config option called client_project_name_override, which is checked before falling back on the current naming convention