Simplify site/node-relative manifest endpoint reference.

[adam-vessey]

Using the provided token should avoid any issues with URL schemes or hostnames or ports and so on.

What does this Pull Request do?

Use the built token instead of manually requiring it to be rebuilt.

• Related GitHub Issue: (link)

• Other Relevant Links: (Google Groups discussion, related pull requests,
  Release pull requests, etc.)

What's new?

Uses the [node:url:unaliased:absolute] to build out the base URL to the node. This token is presently provided by the "Token" module (between https://git.drupalcode.org/project/token/-/blob/8.x-1.x/token.tokens.inc#L56, https://git.drupalcode.org/project/token/-/blob/8.x-1.x/token.tokens.inc#L369-373 and https://git.drupalcode.org/project/token/-/blob/8.x-1.x/token.tokens.inc#L361-364), on which this module is already dependent (

islandora_mirador/islandora_mirador.info.yml

Line 9 in 33843dc

- token:token

)

How should this be tested?

A description of what steps someone could take to:

• Reproduce the problem you are fixing (if applicable)
• Test that the Pull Request does what is intended.
• Please be as detailed as possible.
• Good testing instructions help get your PR completed faster.

Documentation Status

• Does this change existing behaviour that's currently documented?
• Does this change require new pages or sections of documentation?
• Who does this need to be documented for?
• Associated documentation pull request(s): ___ or documentation issue ___

Additional Notes:

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

Interested parties

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

[rosiel]

100%. We could change the example text in the form element's description, too?
https://github.com/Islandora/islandora_mirador/blob/2.x/src/Form/MiradorConfigForm.php#L63