Plugin authors are allowed to omit the function name in the `ep.json`
parts definition. For example:
```
{
"parts": [
{
"name": "ep_example",
"hooks": {
"authenticate": "ep_example",
"authFailure": "ep_example"
}
}
]
}
```
If omitted, the function name is assumed to be the same as the hook
name. Before this change, `hook_fn_name` for the example hooks would
both be `/opt/etherpad-lite/node_modules/ep_example`. Now they are
suffixed with `:authenticate` and `:authFailure`. This improves
logging, and it makes it possible to use `hook_fn_name` to uniquely
identify a particular hook function.
