agent: Fix a stop discovery channel issue

[diconico07]

What this PR does / why we need it:
The stop discovery channel is shared by all Configuration resources of a given discovery handler endpoint, this channel was used without giving any context of the targeted DiscoveryOperator, leading to a stop of discovery for all Configurations when a Configuration is modified or deleted.

This commit makes the stop discovery channel send the concerned Configuration ID (namespace + name) on the channel, allowing to filter out requests targeting another DiscoveryOperator, the channel is still shared so the cases where we really want to stop discovery for all Configurations still works.

Fixes #601

Special notes for your reviewer:
Currently in draft as I still need to add some tests

If applicable:

• this PR has an associated PR with documentation in akri-docs
• this PR contains unit tests
• added code adheres to standard Rust formatting (cargo fmt)
• code builds properly (cargo build)
• code is free of common mistakes (cargo clippy)
• all Akri tests succeed (cargo test)
• inline documentation builds (cargo doc)
• all commits pass the DCO bot check by being signed off -- see the failing DCO check for instructions on how to retroactively sign commits

[kate-goldenring]

It's been awhile since I've looked at this, but aren't we creating a discovery operator for each configuration, regardless of whether they have a shared Discovery Handler / protocol?

akri/agent/src/util/config_action.rs

Line 256 in 54d5584

let (stop_discovery_sender, _): (broadcast::Sender<()>, broadcast::Receiver<()>) =

[diconico07]

We indeed create a discovery operator per configuration, but the stop_discovery_sender you highlight here triggers a stop_all_discovery from the operator, that will iterate over the discovery handler's endpoints to tell each of them to stop discovery.

akri/agent/src/util/discovery_operator.rs

Lines 97 to 98 in 54d5584

	for (endpoint, dh_details) in discovery_handler_details_map.clone() {
	match dh_details.close_discovery_handler_connection.send(()) {

This is needed as we do an internal_do_discover per handler's endpoint (eventually do_discover_on_discovery_handler calls it).

akri/agent/src/util/discovery_operator.rs

Lines 601 to 616 in 54d5584

	for (endpoint, dh_details) in discovery_handler_details_map.clone() {
	trace!(
	"do_discover - for {} discovery handler at endpoint {:?}",
	config.spec.discovery_handler.name,
	endpoint
	);
	let discovery_operator = discovery_operator.clone();
	let kube_interface = kube_interface.clone();
	discovery_tasks.push(tokio::spawn(async move {
	do_discover_on_discovery_handler(
	discovery_operator.clone(),
	kube_interface.clone(),
	&endpoint,
	&dh_details,
	)
	.await

And as the discovery_handler_map (and thus the close_discovery_handler_connection) is shared at agent level, we need to do it this way.
We could also have another broadcast channel at operator's level that is not shared between operators, but we would still need the shared one to correctly handle endpoint changes, so I found it easier this way.

[diconico07]

@bfjelds I added/modified the comments, please tell me if it better now