feat: add opamp controller extension

[albertlockett]

Change Summary

Adds initial implementation of OpAMP Agent Controller Extension.

Design doc can be found in #3388

Adds:

• controller extension
• OpAMP proto definitions & prost generated structs

Currently only works with websocket.

Followups will need to include:

• plain HTTP transport (plain meaning traditional HTTP request/response, not necessarily plaintext)
• mTLS
• connection setting management (this is ignored)
• metrics collection

Currently this lives in the controller crate. I wasn't sure where was the right place for this, and hesitated between controller or core-nodes. Happy to move if anyone has feelings/suggestions

What issue does this PR close?

• Relates to OpAMP Agent Controller Extension #3387

How are these changes tested?

Are there any user-facing changes?

Changelog

• Added a .chloggen/*.yaml entry
• This PR is a chore (indicated in title)
• This is a documentation-only PR.

[Copilot]

Pull request overview

Adds an initial Rust implementation of an OpAMP Agent Controller Extension for the OTAP Dataflow engine, enabling remote engine config updates and status reporting over WebSocket (with future transport/security follow-ups noted in the PR description).

Changes:

• Introduces a new opamp controller extension module with config validation, WebSocket session loop, and status/config exchange logic.
• Adds OpAMP protobuf generation and commits the generated Rust bindings, backed by a new proto/opamp-spec submodule.
• Adds test utilities and integration-style tests (mock OpAMP WebSocket server) plus required Rust dependencies.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
rust/otap-dataflow/xtask/src/genproto.rs	Extends proto generation to compile OpAMP protos into the controller extension’s proto module.
rust/otap-dataflow/crates/controller/src/lib.rs	Exposes the new controller extension module publicly.
rust/otap-dataflow/crates/controller/src/extension.rs	Introduces the controller extension module entry point (pub mod opamp).
rust/otap-dataflow/crates/controller/src/extension/opamp/mod.rs	Implements the OpAMP controller extension runtime (session state, message handling, reconciliation, tests).
rust/otap-dataflow/crates/controller/src/extension/opamp/config.rs	Adds extension configuration types and endpoint/backoff validation.
rust/otap-dataflow/crates/controller/src/extension/opamp/consts.rs	Defines component health status string constants used in OpAMP health reporting.
rust/otap-dataflow/crates/controller/src/extension/opamp/error.rs	Defines error types for OpAMP config validation failures.
rust/otap-dataflow/crates/controller/src/extension/opamp/util.rs	Adds an exponential backoff utility (with jitter) used for reconnect/retry behavior.
rust/otap-dataflow/crates/controller/src/extension/opamp/test/util.rs	Adds a mock ControlPlane and mock OpAMP WebSocket server helpers for tests.
rust/otap-dataflow/crates/controller/src/extension/opamp/proto/mod.rs	Adds module wiring for the generated OpAMP protobuf bindings.
rust/otap-dataflow/crates/controller/src/extension/opamp/proto/opamp.proto.v1.rs	Adds generated Rust types for OpAMP protobuf messages.
rust/otap-dataflow/crates/controller/Cargo.toml	Adds dependencies needed by the extension and its tests (WebSocket, prost, axum, etc.).
rust/otap-dataflow/Cargo.toml	Updates workspace dependency versions/features for axum websockets and adds tungstenite-related crates.
rust/otap-dataflow/Cargo.lock	Locks new dependency additions (including multiple tokio-tungstenite/tungstenite versions).
.gitmodules	Adds proto/opamp-spec as a git submodule to source OpAMP protobuf definitions.

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[codecov]

Codecov Report

❌ Patch coverage is 70.04582% with 523 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.15%. Comparing base (1a3f044) to head (7f7a5c3).
⚠️ Report is 6 commits behind head on main.

❌ Your patch check has failed because the patch coverage (70.04%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3410      +/-   ##
==========================================
- Coverage   86.23%   86.15%   -0.09%     
==========================================
  Files         741      746       +5     
  Lines      292447   294595    +2148     
==========================================
+ Hits       252203   253819    +1616     
- Misses      39720    40252     +532     
  Partials      524      524              

Components	Coverage Δ
otap-dataflow	87.19% <70.04%> (-0.11%)	⬇️
query_engine	89.58% <ø> (ø)
otel-arrow-go	52.45% <ø> (ø)
quiver	92.19% <ø> (ø)

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[lalitb]

Now that we advertise AcceptsRestartCommand, should this be wired to a real agent/process restart?

[lalitb]

Thanks for adding the WebSocket close frame. I think this still misses the OpAMP part though: before the close frame, the client should send an AgentToServer message with agent_disconnect set. Right now this only sends the WebSocket Close frame, so the server still does not receive the OpAMP disconnect message.

[albertlockett]

I'm sorry about that Lalit, you're right. I should have read your previous feedback more carefully!

This has been corrected here: 7f7a5c3

[cijothomas]

lets have a working minimal file in the configs directory.