Implement error handling

[declark1]

This PR implements initial error handling using 3 layers of errors:

1. clients::Error is a low-level error that wraps grpc and http client errors.
   • Implements status_code() method to return the actual (http client) or mapped (grpc client) http status code. This is useful for pattern-matching specific types of errors.
2. orchestrator::Error contains variants for issues that may arise during processing of tasks, such as DetectorNotFound, DetectorRequestFailed, etc. We can extend this as-needed.
3. server::Error is a high-level error returned to the caller, enabling them to react accordingly to validation and not found errors from the orchestrator and downstream services.
   • Implements axum::IntoResponse to return 422 for validation-type errors (with a detailed message), 404 for not found errors, and 500 (with generic “unexpected error” message) for other errors.

     /// High-level errors to return to clients.
     #[derive(Debug, thiserror::Error)]
     pub enum Error {
         #[error("{0}")]
         Validation(String),
         #[error("{0}")]
         NotFound(String),
         #[error("unexpected error occured while processing request")]
         Unexpected,
     }
     
     impl From<orchestrator::Error> for Error {
         fn from(error: orchestrator::Error) -> Self {
             use orchestrator::Error::*;
             match error {
                 DetectorNotFound { .. } => Self::NotFound(error.to_string()),
                 DetectorRequestFailed { error, .. }
                 | ChunkerRequestFailed { error, .. }
                 | GenerateRequestFailed { error, .. }
                 | TokenizeRequestFailed { error, .. } => match error.status_code() {
                     StatusCode::BAD_REQUEST | StatusCode::UNPROCESSABLE_ENTITY => {
                         Self::Validation(error.to_string())
                     }
                     StatusCode::NOT_FOUND => Self::NotFound(error.to_string()),
                     _ => Self::Unexpected,
                 },
                 _ => Self::Unexpected,
             }
         }
     }

• Propagates errors from orchestrator tasks
• Logs orchestrator::Error to provide sufficient detail for debugging
• Adds response debug logging statements for chunker/detector/generation client calls
• Updates create_http_clients and create_grpc_clients to panic rather than return Result and updates Client::new methods and orchestrator::create_clients accordingly

Examples:

1. Invalid detector_id provided in request
   Server response:

   {
       "code": 404,
       "details": "detector not found: not_a_model"
   }

   Error log:

   ERROR fms_guardrails_orchestr8::orchestrator: unary task failed request_id=deaba6cc-9d69-43e0-81dc-3c4ab73532a2 error=detector not found: not_a_model
   

2. Cannot connect to chunker service
   Server response:

   {
       "code": 500,
       "details": "unexpected error occured while processing request"
   }

   Error log:

   ERROR fms_guardrails_orchestr8::orchestrator: unary task failed request_id=09108c5b-00ab-47d2-8195-5032e0a43a62 error=chunker request failed for chunker_id=en_chunker: error trying to connect: tcp connect error: Connection refused (os error 61)
   

[evaline-ju]

Thanks for adding the error handling! A few questions

[evaline-ju]

LGTM!

[gkumbhat]

Looks good to me!