Add more common functions to the hubspot_api app

[mbertrand]

There are some functions and tasks in each of our hubspot-enabled applications that are almost identical but that reference the application's specific functions for handling its object models. Some of these could be made more generic (via adding the app_label and model name as input parameters) and centralized here instead, reducing code duplication.

For example, sync_contact_with_hubspot, sync_deal_with_hubspot, and sync_product_with_hubspot exist in xpro, mitxonline, and bootcamps, but could potentially be replaced by something like this in ol-django/hubspot_api:

def get_hubspot_function(func_name: str) -> Callable:
    """Given a string like my_app.api.do_something, return that function"""
    func_parts = func_name.split(".")
    func = apps.get_app_config(func_parts[0]).module
    for i in range(1, len(func_parts)):
        func = getattr(func, func_parts[i])
    return func


def sync_object_with_hubspot(
        object_id: int,
        msg_func: str,
        app_label: str,
        model_name: str,
        hubspot_type: str
) -> SimplePublicObject:
    """
    Sync a django object with a hubspot object

    Args:
        object_id(int): The django object id
        msg_func(str): The name of function that will generate the request message body (<app>.<module>.<function>)
        app_label(str): The app label for the object model
        model_name(str): The object model name
        hubspot_type(str): The hubspot object type (contact, deal, etc)

    Returns:
        SimplePublicObject: The hubspot object
    """
    body = get_hubspot_function(msg_func)(object_id)
    content_type = ContentType.objects.get_by_natural_key(app_label, model_name)

    return upsert_object_request(
        content_type, hubspot_type, object_id=object_id, body=body
    )