'This is an opaque unique identifier that the TC guarantees will be unique
within the TC for every placement of the link.
If the tool / activity is placed multiple times in the same context,
each of those placements will be distinct.
This value will also change if the item is exported from one system or
context and imported into another system or context.
This parameter is required.
Example:  u\'edx.org-i4x-2-3-lti-31de800015cf4afb973356dbe81496df\'
Hostname, edx.org,
makes resource_link_id change on import to another system.
Last part of location, location.name - 31de800015cf4afb973356dbe81496df,
is random hash, updated by course_id,
this makes resource_link_id unique inside single course.
First part of location is tag-org-course-category, i4x-2-3-lti.
Location.name itself does not change on import to another course,
but org and course_id change.
So together with org and course_id in a form of
i4x-2-3-lti-31de800015cf4afb973356dbe81496df this part of resource_link_id:
makes resource_link_id to be unique among courses inside same system.'

def get_resource_link_id(self):

    return unicode(urllib.quote('{}-{}'.format(self.system.hostname, self.location.html_id())))
