Use refresh API to update synonyms

[lonvia]

OpenSearch has support for dynamic update of analyzers. This would significantly simplify the dynamic installation of the synonym list.

[lonvia]

Played around with this. Dynamic updates require the Index Management Plugin, which cannot be added by simply including a dependency. It needs to be installed as a plugin in the data directory. This used to be a pain point in the ES installation and I was quite happy to get rid of it. It also seems to be a rather heavy dependency for such a small feature.