### Description

The `sendRequest` method is asynchronous and notifies a 
`TransportResponseHandler` when it completes the excecution
(successfully or unsuccessfully). 

When opening the connection we only catch `NodeNotConnectedException`
( https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/transport/TransportService.java#L719 ) which is currently fine as no implementations
throw other type of exception however, it'd be best to catch `Exception` here
so the `handler` gets notified of potential exceptions (as opposed to the caller
having to `try/catch` the call to `sendRequest`)
server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java
null,
            Map.of(coordinator.getLocalNode().getId(), coordinator.getClusterFormationState().getDescription())
        );
        return new CoordinationDiagnosticsResult(CoordinationDiagnosticsStatus.RED, summary, details);
    }
    /**
     * Returns the master eligible nodes as found in this node's Coordinator, plus the local node if it is master eligible.
     * @return All known master eligible nodes in this cluster
     */
    private Collection<DiscoveryNode> getMasterEligibleNodes() {
        Set<DiscoveryNode> masterEligibleNodes = new HashSet<>();
        coordinator.getFoundPeers().forEach(node -> {
            if (node.isMasterNode()) {
                masterEligibleNodes.add(node);
            }
        });
        
        if (clusterService.localNode().isMasterNode()) {
            masterEligibleNodes.add(clusterService.localNode());
        }
        return masterEligibleNodes;
    }
    /**
     * This returns true if this node has seen a master node within the last few seconds
     * @return true if this node has seen a master node within the last few seconds, false otherwise
     */
    private boolean hasSeenMasterInHasMasterLookupTimeframe() {
        return masterHistoryService.getLocalMasterHistory().hasSeenMasterInLastNSeconds((int) nodeHasMasterLookupTimeframe.seconds());
    }
    /*