Add Indexing Endpoint

Context

As part of gitlab-org/gitlab-zoekt-indexer#105 (closed), we are adding an HTTP Client for GKG on Zoekt Side.

This issue about implementing the corresponding full indexing endpoint on GK Indexer Service. Refer to gitlab-org/gitlab-zoekt-indexer!643 for the implemented API requests (might change until it's merged).

Note that there was already a related code when we used indexer through FFI. This code was removed in !315 (merged), but it's worth checking crates/indexer/src/deployed/executor.rs in this MR because it might be re-used.

POCs

there is already @michaelangeloio's POC, a lot can be re-used for adding this endpoint
There is also another POC from @OmarQunsulGitlab : !254

CC: @jprovaznik

Edited Sep 17, 2025 by Jan Provaznik