Rework async binary metadata process

Binary Metadata Async

Issues

The process async was not possible to be executed in this mode for the following reasons: (the test updated was offuscating the error)

The context data and two sync listeners

The feature is:

passing context data set in a Document via a listener on beforeModification
retrieving those context data in a listener on documentModified

But

The context data is flushed by the AbstractSession#saveDocument when a read document is executed before the documentModified event fire.

So the flag is always empty or null for starting the binary metadata worker.

See for instance https://github.com/nuxeo/nuxeo-binary-metadata/commit/d93736602b048a19093da645fe5013c8ccf09325

The dirty properties

We cannot follow the rules in an async way: the properties or blob are never dirty.

Conclusion - Solution

We should:

• Keep only the first listener org.nuxeo.binary.metadata.internals.listeners.BinaryMetadataSyncListener doing all the dispatch and process.
• Execute the sync process as it is.
• Execute the async process and passing to the worker all Dirty information found on the documents to do the mapping correctly.

For documentation, should be added:

• A sequence diagram
• A rules schema