Can't list all properties of a Blob in Freemarker (ClassCastException on ?keys)

This is the same as #NXP-10101 but for BlobTemplate, and probably

When trying to list all properties of a Blob (such as doc['file:content']) in a Freemarker template view (ex. for logging purpose) using the ?keys builtin (since a Blob is a Hash extension in Freemarker), there is a ClassCastException (see below).

To patch it, reimplement BlobTemplate.keys()
from
return (TemplateCollectionModel) wrapper.wrap(getRawKeys());
to
return new CollectionAndSequence(new SimpleSequence(getRawKeys(), wrapper));
and it should do the trick.

RenderingException: java.lang.ClassCastException: freemarker.template.SimpleSequence cannot be cast to freemarker.template.TemplateCollectionModel
at org.nuxeo.ecm.platform.rendering.fm.FreemarkerEngine.render(FreemarkerEngine.java:200)
at org.nuxeo.ecm.webengine.model.impl.AbstractWebContext.render(AbstractWebContext.java:583)
... 59 more
Caused by: java.lang.ClassCastException: freemarker.template.SimpleSequence cannot be cast to freemarker.template.TemplateCollectionModel
at org.nuxeo.ecm.platform.rendering.fm.adapters.BlobTemplate.keys(BlobTemplate.java:56)
at freemarker.core.BuiltIn$keysBI._getAsTemplateModel(BuiltIn.java:598)
at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
at freemarker.core.Expression.getStringValue(Expression.java:93)
at freemarker.core.DollarVariable.accept(DollarVariable.java:76)