[DOCS] Remove _term and _time agg order keys

[jrodewig]

Adds an 8.0 breaking change for the removal of the _term and _time
agg order keys.

Relates to #39450

Preview

https://elasticsearch_78209.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/migrating-8.0.html#breaking_80_aggregations_changes

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)

[not-napoleon]

Should we (do we?) support this in 7.x REST compatibility mode? IIRC that didn't exist when we dropped these sort keys

[nik9000]

Should we (do we?) support this in 7.x REST compatibility mode? IIRC that didn't exist when we dropped these sort keys

I think we probably should, yeah. I think the docs change is still right even so.

[jrodewig]

Should we (do we?) support this in 7.x REST compatibility mode? IIRC that didn't exist when we dropped these sort keys

Thanks for calling this out @not-napoleon. It looks like we do support them with version compatibility headers. However, I don't think we need to call that out in this breaking change. IMO that's sorta the same as using a previous version of the API.

elasticsearch/server/src/main/java/org/elasticsearch/search/aggregations/InternalOrder.java

Line 579 in 979f297

if (parser.getRestApiVersion() == RestApiVersion.V_7 && ("_term".equals(orderKey) || "_time".equals(orderKey))) {

[not-napoleon]

Yes, sorry, docs change is fine. I think we just need to also do REST compatibility.

[nik9000]

It looks like we do support them with version compatibility headers.

Nice! I'd assumed we dumped them. I'm so happy we still have that. Now I can GC _term and _time from my brain again.