Indexer instances are the ones who know how to connect
to elasticsearch and which index should the query should
be executed on

As for ES "id" parameters, "doc_type" should be customizable,
there is no reason why es document type should match cw_etype

Default is to use 'eid' but one may want to use something
else (stable id, ark, etc.)

closes #17079908

For optimization sake, just make sure the original rset
fetches everyting or use complete=True but relying on
cw_attr_cache will cause very obscure bugs

closes #17079907

* get rid of CUSTOM_ATTRIBUTES. Replace it with IFullTextIndexSerializable adapter `custom_indexable_attributes`
  attribute;
* FullTextIndexSerializable.serialize method : default complete value is now True*


closes #17079905

It's not used (and therefore not real-life-tested) anywhere
and current implementation is known to be partial and a bit
hard to maintain.

(closes #17071989)

Otherwise we would overwrite the "mappings" entry

In order to be sure that child / parent relation is set

[optimisation] cwuri need to be in RQL, otherwise it *really* slows down the indexing when cw accesses entity.cw_uri.

Update using entity.cw_attr_cache should be enough, no need to loop over attributes again

Also : ccplugin - generator serves all actions, not split up by type
       es.py - add CUSTOM_ATTRIBUTES mechanism

`indexable_attributes` in yams return only String and Bytes

`esearch` view relies on this attr