provide custom event params via extra attribute

[mahenzon]

Custom method can be now declared for events via extra config. Sure it can be just a POST method, but why not giving some more options, plus this extra can be loaded with other stuff later.

For example, custom url_suffix can be provided too. So instead of /user/{id}/event_update_user_online_status/ url will be /user/{id}/update_online/.

from flask import request
from combojsonapi.event.resource import EventsResource


class UserDetailEvents(EventsResource):
    def event_update_user_online_status(self, *args, **kwargs):
        # language=YAML
        """
        ---
        # some description
        """
        result = some_custom_stuff_to_do(kwargs, request.json)
        return result

    event_update_user_online_status.extra = {
        "method": "PUT",
        "url_suffix": "update_online",
    }