[ENG-9820]: cleanup and delete dead ES2 code

[ihorsokhanexoft]

Ticket

https://openscience.atlassian.net/browse/ENG-9820

Purpose

After removing v1/v2 search endpoints, there is a lot of unused code that can be removed

Changes

Remove legacy code

IT IS HIGHLY RECOMMENDED TO REVIEW THIS PULL REQUEST COMMIT BY COMMIT

[Vlad0n20]

Clean, well-scoped deletion. One missed cleanup: CoreScopes.SEARCH = 'search_read' at oauth_scopes.py:136 is left as a dead definition after its only usages are removed — should be deleted alongside ADVANCED_SEARCH. Also worth confirming whether /explore/ and /activity/ need infrastructure-level redirects before this merges. Everything else looks good.

[ihorsokhanexoft]

Clean, well-scoped deletion. One missed cleanup: CoreScopes.SEARCH = 'search_read' at oauth_scopes.py:136 is left as a dead definition after its only usages are removed — should be deleted alongside ADVANCED_SEARCH. Also worth confirming whether /explore/ and /activity/ need infrastructure-level redirects before this merges. Everything else looks good.

But CoreScopes.SEARCH is used in BaseSearchView that many views inherit from:

So why should we remove it?

[Vlad0n20]

LGTM!