Adding Samvera::Derivatives interface and Hyrax shim

[jeremyf]

Adding Samvera::Derivatives for interface discussion

53e80f5

This commit begins to define an interface for the separation of concerns
regarding the long-standing implementation of Hydra::Derivatives and
Hyrax::FileSetDerivativesService as those relate to the
existence of pre-existing derivatives.

This does not address the implementation details related to Bulkrax
handling this work. I would instead assume that Bulkrax would implement
a subclass(es) Samvera::Derivatives::FileLocator::Strategy, which
would in turn address the specific needs and implementation details.

As I've explored the implementations, a challenge of Hydra::Derivatives
is that is combines the concern of finding the derivative (by making it)
and applying that derivative to the corresponding file set.

Also, there is a higher level concern that is not addressed in this
implementation; namely what are the derivatives of concern for a
given FileSet; something that is likely based on the mime_type of the
original file and metadata from the parent work.

Why not create another gem?

1. The immediate need is Bulkrax related.
2. The plumbing is laid for Bulkrax's test suite.
3. We probably don't need another gem to triangulate for a general
   solution.

That said, I am name spacing this interface in Samvera so if we find
it useful we can extract a samvera-derivatives gem. After all, not
everyone's going to want Bulkrax.

Why not put this in Hyrax?

1. Because Bulkrax works across many different Hyrax versions. Thus by
   being in Bulkrax it is generally more available than if it were in
   Hyrax; something which we'd need to backport.

An advantage of establishing the interface is that work can be done to
now "fan out". That is someone can work on a locator strategy while
another works on the applicator strategy.

Related to:

• EPIC: Introduce Concept and Handling of Existing Derivatives #760
• Conditional Derivatives: Inject module into registered to override function notch8/utk-hyku#343

Introducing location concept to Samvera::Derivatives

42df4df

Prior to this commit, I was passing an array of strings back from the
locator. With that pathway, I was ignoring how the existing
Hyrax::FileSetDerivativesService would likely be used as a fallback.

With this commit, I'm beginning to account for how that interaction
would be; in part by focusing on a known use case and building the
interactions accordingly.

This commit stencils in the expected behavior in what I think is
adequate to convey intention and design.

Related to:

• EPIC: Introduce Concept and Handling of Existing Derivatives #760
• Conditional Derivatives: Inject module into registered to override function notch8/utk-hyku#343

Adding Samvera::Derivatives::Hyrax consideration

e33e454

With this commit, I begin demonstrating how the original configuration
can be leveraged to do the derivative work. This still assumes a
configuration for derivatives; something that I continue to punt on
until I have more concrete code that I can further build from.

Related to:

• EPIC: Introduce Concept and Handling of Existing Derivatives #760
• Conditional Derivatives: Inject module into registered to override function notch8/utk-hyku#343

[jeremyf]

This may not be the best place for this switching logic; I suspect there's another class that's somewhat itching to emerge.

[orangewolf]

@jeremyf I do think having this work in Hyrax is the right thing. I get doing it in bulkrax temporarily, but I think it needs to be very temporary. The process should work if you are direct creating the items in the interface and it should hook in to the actor stack. Bulkrax flow should know nothing about it at all because it just passes the correctly formatted thing to the actor stack.

[orangewolf]

I’m curious why this isn’t happening in iiif-print where we already massively modify the derivative process?

[jeremyf]

Moving this to IIIF Print

[jeremyf]

@orangewolf Bulkrax needs to know about it in that it needs a mechanism for capturing remote URLs; perhaps there's no necessary knowledge but those are not quite related to Bulkrax.