feat(kms-connector): shared otlp context

[eudelins-zama]

Closes https://github.com/zama-ai/fhevm-internal/issues/475

Here's what it looks like:

Only issue is that the parent span's duration is not shown as the sum of the 3 child spans. This is because the handle_gateway_event span is automatically closed when the function exit (implementation of the tracing crate).

I spent some time digging this, and the only way I see to resolve this would be to implement a way for tx-sender to warn gw-listener that he finished its job (grpc call for instance), and to only exit the handle_gateway_event when the gw-listener receive the ping from the tx-sender. It might be a bit overkill for now, I asked @leventdem about this and we decided to postpone this for now, and merge this as it is.

[Copilot]

Pull Request Overview

This PR implements shared OTLP (OpenTelemetry) context propagation across the KMS connector services to enable distributed tracing. The changes add tracing context to database models and propagate it through the event processing pipeline from gateway events to KMS responses.

• Refactored GatewayEvent and KmsResponse from enums to structs containing kind and otlp_context fields
• Added PropagationContext type for serializing/deserializing OpenTelemetry trace context
• Updated database schema to store OTLP context in all event and response tables

Reviewed Changes

Copilot reviewed 22 out of 38 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
kms-connector/crates/utils/src/types/mod.rs	Made gw_event and kms_response modules public and exported new types
kms-connector/crates/utils/src/types/kms_response.rs	Refactored KmsResponse to struct with kind and otlp_context fields
kms-connector/crates/utils/src/types/gw_event.rs	Refactored GatewayEvent to struct with kind and otlp_context fields
kms-connector/crates/utils/src/monitoring/otlp.rs	Added PropagationContext type for OTLP context serialization
Multiple test files	Updated tests to work with new struct-based event/response types
Database migration	Added otlp_context columns to all event and response tables

Files not reviewed (15)

• kms-connector/.sqlx/query-1a43a1973631354ba7c92764223b8acaaba30982fbf37619f9982ee5adac8b04.json: Language not supported
• kms-connector/.sqlx/query-2006d0c6aa7ad4945af0ae9d6fa99d64f62543158c13f34b0096e56357539ba1.json: Language not supported
• kms-connector/.sqlx/query-3632e17b59f53983cc2f385caf05b37d8f730eef72776bee1de3356a605b0714.json: Language not supported
• kms-connector/.sqlx/query-39c059ee786b91cdda4288eecc1af69b8166dc79e4754ca74ee373c1cfaa5066.json: Language not supported
• kms-connector/.sqlx/query-3c1d97d4cb3eb8a3c1c3f5dccc6beca0425152e8b77ec40041502f0b8e57c058.json: Language not supported
• kms-connector/.sqlx/query-870dd150166705cc721622e07679ab492649be1199934f92708fece4df95b8ff.json: Language not supported
• kms-connector/.sqlx/query-8999cf2e601ad18a848f118ca5131dc3e9a5d4176f5f92bbceec770043c36baf.json: Language not supported
• kms-connector/.sqlx/query-b349bf7c7e98d7cb858654f939fe6733b7fb1774e80cdc0b1a48cfa5cde4c521.json: Language not supported
• kms-connector/.sqlx/query-cfa5dec1bb7a0a586b6822fd222bb518762f67fd7484c4efd1fb5320268f4341.json: Language not supported
• kms-connector/.sqlx/query-d2b33c24cd185f97f5810a4b3da91565c87fed9d1697d651f5e51ffbba756bd6.json: Language not supported
• kms-connector/.sqlx/query-d3238c10e01dbc5d2c06e409a9af2018b4770de5ee42126407a8276c7f54145f.json: Language not supported
• kms-connector/.sqlx/query-d6df03a7c7617fb4ac99be6a98fd7fa4368b8b78709f3b07fba773d49ae219fe.json: Language not supported
• kms-connector/.sqlx/query-daa213ba26085a6b864c60726c3e8a4d548bfd09d0791505fc3db89a6ee7f343.json: Language not supported
• kms-connector/.sqlx/query-f63cbf98d0c26a3ffbd4c9080549ac15911c81f352d86f33ee79c0b244765ac7.json: Language not supported
• kms-connector/.sqlx/query-fb044e1f8fc652401b00b59ef041debded52e491cf85e3c23e660dd2af5380aa.json: Language not supported

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[dartdart26]

Looks good!