Update Node table code. Add simple unit test

internal/graph/model/models.go

@@ -4,20 +4,3 @@
 // license that can be found in the LICENSE file.
 
 package model
-
-import (
-	"github.com/ClusterCockpit/cc-lib/schema"
-)
-
-type Node struct {
-	ID              int64
-	Hostname        string                 `json:"hostname"`
-	Cluster         string                 `json:"cluster"`
-	SubCluster      string                 `json:"subCluster"`
-	RunningJobs     int                    `json:"jobsRunning"`
-	CpusAllocated   int                    `json:"cpusAllocated"`
-	MemoryAllocated int                    `json:"memoryAllocated"`
-	GpusAllocated   int                    `json:"gpusAllocated"`
-	NodeState       schema.NodeState       `json:"nodeState"`
-	HealthState     schema.MonitoringState `json:"healthState"`
-}