Function validate_and_resolve_user_attribution_grpc 

pub fn validate_and_resolve_user_attribution_grpc(
    metadata: &MetadataMap,
) -> Result<UserAttribution, Box<Status>>

Validate and resolve user attribution from gRPC metadata

This function prevents user impersonation by validating x-user-id and x-user-email headers against the authenticated user’s identity:

• OIDC user tokens: User identity MUST match token claims (no impersonation allowed)
• API keys/service accounts: Can act on behalf of users (delegation allowed)
• Unauthenticated requests: Pass through client-provided attribution

Header values support percent-encoded UTF-8 for international characters. Invalid headers are handled gracefully with logging.

Arguments

• metadata - gRPC metadata map (tonic::metadata::MetadataMap) containing authentication and attribution headers

Returns

Returns Ok(UserAttribution) containing:

• user_id: The resolved user identifier
• user_email: The resolved user email
• user_name: The display name from x-user-name header (if provided)
• service_account: Some(name) when delegation is being used, None otherwise

Errors

Returns Err(Box<Status::PermissionDenied>) if an OIDC user attempts to impersonate another user.

Example

use micromegas_auth::user_attribution::validate_and_resolve_user_attribution_grpc;
use tonic::metadata::MetadataMap;

let mut metadata = MetadataMap::new();
metadata.insert("x-auth-subject", "alice@example.com".parse().unwrap());
metadata.insert("x-auth-email", "alice@example.com".parse().unwrap());
metadata.insert("x-allow-delegation", "false".parse().unwrap());
metadata.insert("x-user-id", "alice@example.com".parse().unwrap());

let result = validate_and_resolve_user_attribution_grpc(&metadata);
assert!(result.is_ok());