Replace space by + in tags

The tag service sanitizes tag names and removes all space characters.

This is an issue because words get concatenated and are not searchable anymore. This defeats the purpose of tagging images.

Ex: "mountain range" becomes "mountainrange" which won't match searches for either mountain or range

Replacing space by + is the strategy that is used in the nuxeo-vision plugin

Check in org.nuxeo.ai.functions.StoreLabelsAsTags