Fixes #976 and #578, and replaces #978.

@dbanty please choose your preferred approach between this and PR #987.

The original issue is that `openapi-python-client` throws `incorrect
path templating` warnings when the path has a parameter with a hyphen
and consequently fails to generate the endpoints.

---

The first commit ensures that hyphens are recognised as allowed
delimiters in parameter path names. This allows the endpoints to be
generated.

However, this generates lines like these:

```python
def _get_kwargs(
    user_id: int,
) -> Dict[str, Any]:
    _kwargs: Dict[str, Any] = {
        "method": "post",
        "url": "/activitypub/user-id/{user-id}/inbox".format(user-id=user_id,),
    }
    return _kwargs
```

Since Python variable names cannot contain hyphens, the `user-id`
parameter name here will trigger errors (starting with `ruff`).

---

The second commit replaces parameter names with their `python_name` in
`__init__.py` and passes the modified path to
`templates/endpoint_module.py.jinja`.

This fixes the issue and allows endpoints to be generated correctly. 

---

#987 is a different option for the second commit which instead creates a
custom Jinja filter in `utils.py` and so that the parameter names in
`endpoint.path` can be converted to their python names directly in
`templates/endpoint_module.py.jinja`.

Both approaches are equivalent and have been tested with different
parameter names (snake case, camel case, kebab case, mixed).

---------

Co-authored-by: harabat <[email protected]>
Co-authored-by: Dylan Anthony <[email protected]>
Co-authored-by: Dylan Anthony <[email protected]>