✨ Add transformations during request forwarding...

[davidfestal]

Summary

Add a mechanism that :

• provides transformations during request forwarding
• also allows transforming the request result.

This PR is the first part of PROOF PR #1239, which implements most of the EPIC Multi-SyncTarget syncing and coordination controllers.

Thus this PR should be reviewed with the wider context and use-case in mind.

Related issue(s)

#1992

[stevekuznetsov]

Without seeing this used somewhere, it's not entirely clear to me how to evaluate the client.

[davidfestal]

Without seeing this used somewhere, it's not entirely clear to me how to evaluate the client.
Sure I should have given precise pointers in the PR description.

You can see it in action in the PROOF PR:

• The SyncerResourceTransformer implements the ResourceTransformer interface in order to, among other things, manage the Syncer-specific Views and the Syncer transformations
• A transforming client based on this SyncerResourceTrasformer is then simply passed as the dynamic client passed to the Syncer Virtual Workspace StorageBuilder

This is the first use of it, but @jmprusi is already working on using the same transformingClient mechanism, but with a distinct ResourceTransformer implementation, to settle basic transformations in the new upcoming Upsyncer Virtual Workspace (basic transformations are required during UpSyncing for the storage use-case at first, but also later on for Pod upsyncing).

[jmprusi]

/lgtm

[davidfestal]

/approve

[openshift-ci]

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[davidfestal]

Since it doesn't impact any other place in the code, I approved the PR myself (though I created it) to unblock further work, especially PR #2180.

[davidfestal]

cc @sttts