Add spec for project routing CRUD REST API endpoints

[alexey-ivanov-es]

Elasticsearch PR: elastic/elasticsearch#139634

[github-actions]

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

API	Status	Request	Response
esql.delete_view	➕ 🟢	1/1	0/0
esql.get_view	➕ 🟢	6/6	0/0
esql.put_view	➕ 🟢	2/2	0/0
project_routing.create	➕ ⚪	Missing test	Missing test
project_routing.create_many	➕ ⚪	Missing test	Missing test
project_routing.delete	➕ ⚪	Missing test	Missing test
project_routing.get	➕ ⚪	Missing test	Missing test
project_routing.get_many	➕ ⚪	Missing test	Missing test

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

[flobernd]

Looks good, thank you 🙂 Just a few minor questions/comments.

[flobernd]

Is this class named the same in the Elasticsearch code base? I personally would have used ProjectRouting as the class name since the expression is only a part of it, but if it's the same in Elasticsearch, let's keep it as is 🙂

[l-trotta]

I'm looking at the server code (in serverless) and it seems like every class there is actually called SomethingProjectRoutingExpression, so I'd actually argue all other endpoint classes should be named as closely as possible to what's in the server code

[alexey-ivanov-es]

In the server code it is SavedProjectRoutingExpression, but I think Saved prefix would be confusing in API

[l-trotta]

agree for Saved, I'd keep Expression though

[flobernd]

LGTM! Thanks a lot!