Improve tests and fix some bugs

[ludovicm67]

This PR is doing the following:

• send an empty body message in case of error, this fix some unexpected issues with the use of hijackresponse (that we will try to remove in the future)
• fix an issue in entity renderer plugin for the label loader, where the forEach method is not available due to the replacement of rdf-ext with @zazuko/env
• improve tests for the entity renderer: it's now able to check if it is rendered as HTML also

[changeset-bot]

🦋 Changeset detected

Latest commit: fae8107

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@zazuko/trifid-entity-renderer	Patch
trifid-core	Patch

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