Inner hits should fail when the same name is used multiple times in the same query

[jpountz]

This typically happens if the query contains eg. two inner hits definitions on the same nested path and does not define explicit names for inner hits.

[martijnvg]

Additionally we can maybe also make name option required.

[jpountz]

I think users like the fact that we use a name that is a good description of the join by default. Also most queries should be reasonable and only do one join. So I'd be leaning towards keeping name optional.

[andyb-elastic]

It looks like duplicate names are still allowed in master, both with name explicitly provided or not. This sounds like something we likely still want to do

@elastic/es-search-aggs

[jimczi]

This was implemented in #37645, hence closing