Issue #964: Allow relative paths in IIIF manifests.

[alxp]

GitHub Issue: (link)

What does this Pull Request do?

Adds a configuration option for IIIF manifests to use relative paths for image URLs.

What's new?

Adds a config option to make IIIF manifests use local file paths.

• Does this change add any new dependencies? No
• Does this change require any other modifications to be made to the repository
  (i.e. Regeneration activity, etc.)? No
• Could this change impact execution of existing code? No

How should this be tested?

On an Islandora site set up with Islandora IIIF and paged content, go to a piece of paged content, and's manifest URL, usually node/[node:nid]/book-manifest or .../manifest.

Note the image URLs under canvases > images > resources include URL encoded strings representing the full URL of the image, including the Drupal site host.

Go to the Admin settings page for Islandora IIIF, /admin/config/islandora/iiif

Check the 'Use relative paths' option and save the settings.

Reload the same manifest and inspect the @id elements under canvases > resources and note they don't include the full (encoded) url of the Drupal site but only the relative path.

Documentation Status

• Does this change existing behaviour that's currently documented? No
• Does this change require new pages or sections of documentation? No
• Who does this need to be documented for?
• Associated documentation pull request(s): ___ or documentation issue ___ TK

Additional Notes:

Any additional information that you think would be helpful when reviewing this
PR.

If you want to test this fully including a Cantaloupe stack I can give an example site config and Cantaloupe properties file.

Interested parties

Tag (@ mention) interested parties or, if unsure, @Islandora/committers

[alxp]

Fixed schema indentation and added Advanced field group as requested.