Create URL alias from 7.x object to 8.x object on migration

[mjordan]

This blog post describes how to use the 'url_alias' plugin to create aliases on migration: https://evolvingweb.ca/blog/migrating-aliases-and-redirects-drupal-8. Creating URL aliases from the source to the target object should be optional, however.

Related issue: #822 .

[mjordan]

Following up on the June 26 call, it might be good to define some use cases here for this since there are a number of variations of this functionality. I'll provide a couple.

Title (Goal)	Keep 7.x-style cannonical URLs to objects in place
Primary Actor	Repo Admin
Scope	URLs to objects
Level	Normal
Story	As an admin of an Islandora 8 repo migrated from a 7.x repo, I want all URLs of the pattern /islandora/object/some:pid to lead users of my new repo to get the same object they would have on the 7.x site. My old and new repos will have the same hostname.

[mjordan]

A variation on the previous use case:

Title (Goal)	Keep URL aliases to objects in place
Primary Actor	Repo Admin
Scope	URLs to objects
Level	Normal
Story	As an admin of an Islandora 8 repo migrated from a 7.x repo, I want all URL aliases I defined on my 7.x site to lead users of my new repo to get the same object they would have on the 7.x site. An example alias would be https://digital.lib.sfu.ca/edcartoons-311/avoid-any-misunderstanding-about-little-note-im-writing-it-may-be-valentines-day-you. My old and new repos will have the same hostname.