Async search error handling

[l-trotta]

As discussed in the latest spec meeting, adding exception handling to async search. server code

To reproduce:

POST /non-existing-index/_async_search

[github-actions]

Following you can find the validation changes against the target branch for the APIs.

API	Status	Request	Response
bulk	🟢	578/578 → 577/577	596/596 → 595/595
cluster.put_component_template	🔴	34/38 → 30/34	38/38 → 34/34
field_caps	🟢	74/74 → 70/70	74/74 → 70/70
get	🟢	325/325 → 321/321	322/322 → 318/318
index	🟢	1463/1463 → 1457/1457	1465/1465 → 1459/1459
indices.create	🔴	1435/1463 → 1430/1458	1463/1463 → 1458/1458
indices.get_mapping	🔴	225/225 → 223/223	214/225 → 212/223
indices.put_index_template	🔴	142/166 → 136/160	166/166 → 160/160
search	🔴	2644/2662 → 2641/2659	2662/2662 → 2659/2659

You can validate these APIs yourself by using the make validate target.

[pquentin]

Sorry, I have no idea how to get to this result from the server code. Did you consider creating an AsyncSearchException class since the content appears to be the same in both cases?

[l-trotta]

@pquentin thanks, updated and added reproducible