refactor: replace manual REST endpoint instrumentation with go-gin-prometheus

Replace manual timing instrumentation in individual REST endpoints with
go-gin-prometheus middleware for automatic metrics coverage across all
HTTP endpoints.

Changes:
- Add go-gin-prometheus dependency to provide standard HTTP metrics
- Integrate Prometheus middleware in router for automatic instrumentation
- Remove manual timing code from features, KVM displays, and power endpoints
- Remove unused kvmAPIRequestSeconds metric and RecordAPIRequest function
- Clean up unused time and devices package imports

Benefits:
- Automatic metrics for ALL REST endpoints (not just 3)
- Standard HTTP metrics (duration, status codes, request/response sizes)
- Less repetitive code and improved maintainability
- Keeps all custom KVM connection and data flow metrics

Addresses reviewer feedback in PR #761

Author: nmgaston

go.mod

@@ -59,6 +59,7 @@ require (
 	github.com/ryanuber/go-glob v1.0.0 // indirect
 	github.com/woodsbury/decimal128 v1.4.0 // indirect
 	github.com/zalando/go-keyring v0.2.6 // indirect
+	github.com/zsais/go-gin-prometheus v1.0.2 // indirect
 	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	golang.org/x/exp v0.0.0-20251023183803-a4bb9ffd2546 // indirect
 	golang.org/x/oauth2 v0.30.0 // indirect

go.sum

@@ -269,6 +269,8 @@ github.com/woodsbury/decimal128 v1.4.0 h1:xJATj7lLu4f2oObouMt2tgGiElE5gO6mSWUjQs
 github.com/woodsbury/decimal128 v1.4.0/go.mod h1:BP46FUrVjVhdTbKT+XuQh2xfQaGki9LMIRJSFuh6THU=
 github.com/zalando/go-keyring v0.2.6 h1:r7Yc3+H+Ux0+M72zacZoItR3UDxeWfKTcabvkI8ua9s=
 github.com/zalando/go-keyring v0.2.6/go.mod h1:2TCrxYrbUNYfNS/Kgy/LSrkSQzZ5UPVH85RwfczwvcI=
+github.com/zsais/go-gin-prometheus v1.0.2 h1:3asLqrFltMdItpgr/OS4hYc8pLq3HzMa5T1gYuXBIZ0=
+github.com/zsais/go-gin-prometheus v1.0.2/go.mod h1:iKBYSOHzvGfe2FyGSOC8JSwUA0MITdnYzI6v+aAbw1Q=
 go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJySYA=
 go.opentelemetry.io/auto/sdk v1.1.0/go.mod h1:3wSPjt5PWp2RhlCcmmOial7AvC4DQqZb7a7wCow3W8A=
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.61.0 h1:F7Jx+6hwnZ41NSFTO5q4LYDtJRXBf2PD0rNBkeB/lus=

internal/controller/httpapi/router.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/gin-gonic/gin"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
+	ginprometheus "github.com/zsais/go-gin-prometheus"
 
 	"github.com/device-management-toolkit/console/config"
 	v1 "github.com/device-management-toolkit/console/internal/controller/httpapi/v1"
@@ -21,6 +22,10 @@ func NewRouter(handler *gin.Engine, l logger.Interface, t usecase.Usecases, cfg
 	handler.Use(gin.Logger())
 	handler.Use(gin.Recovery())
 
+	 // Add Prometheus middleware for automatic HTTP metrics
+    p := ginprometheus.NewPrometheus("gin")
+    p.Use(handler)
+
 	// Initialize Fuego adapter
 	fuegoAdapter := openapi.NewFuegoAdapter(t, l)
 	fuegoAdapter.RegisterRoutes()

internal/controller/httpapi/v1/features.go

@@ -2,12 +2,10 @@ package v1
 
 import (
 	"net/http"
-	"time"
 
 	"github.com/gin-gonic/gin"
 
 	dto "github.com/device-management-toolkit/console/internal/entity/dto/v1"
-	"github.com/device-management-toolkit/console/internal/usecase/devices"
 )
 
 func (r *deviceManagementRoutes) getVersion(c *gin.Context) {
@@ -25,12 +23,6 @@ func (r *deviceManagementRoutes) getVersion(c *gin.Context) {
 }
 
 func (r *deviceManagementRoutes) getFeatures(c *gin.Context) {
-	start := time.Now()
-
-	defer func() {
-		devices.RecordAPIRequest(time.Since(start), "amt_features")
-	}()
-
 	guid := c.Param("guid")
 
 	features, _, err := r.d.GetFeatures(c.Request.Context(), guid)

internal/controller/httpapi/v1/kvm.go

@@ -2,22 +2,14 @@ package v1
 
 import (
 	"net/http"
-	"time"
 
 	"github.com/gin-gonic/gin"
 
 	"github.com/device-management-toolkit/console/internal/entity/dto/v1"
-	"github.com/device-management-toolkit/console/internal/usecase/devices"
 )
 
 // getKVMDisplays returns current IPS_ScreenSettingData for the device
 func (r *deviceManagementRoutes) getKVMDisplays(c *gin.Context) {
-	start := time.Now()
-
-	defer func() {
-		devices.RecordAPIRequest(time.Since(start), "kvm_displays")
-	}()
-
 	guid := c.Param("guid")
 
 	settings, err := r.d.GetKVMScreenSettings(c.Request.Context(), guid)

internal/controller/httpapi/v1/power.go

@@ -2,21 +2,13 @@ package v1
 
 import (
 	"net/http"
-	"time"
 
 	"github.com/gin-gonic/gin"
 
 	"github.com/device-management-toolkit/console/internal/entity/dto/v1"
-	"github.com/device-management-toolkit/console/internal/usecase/devices"
 )
 
 func (r *deviceManagementRoutes) getPowerState(c *gin.Context) {
-	start := time.Now()
-
-	defer func() {
-		devices.RecordAPIRequest(time.Since(start), "power_state")
-	}()
-
 	guid := c.Param("guid")
 
 	state, err := r.d.GetPowerState(c.Request.Context(), guid)

internal/usecase/devices/metrics.go

@@ -138,15 +138,6 @@ var (
 		},
 		[]string{"mode"},
 	)
-
-	kvmAPIRequestSeconds = promauto.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "kvm_api_request_seconds",
-			Help:    "Time for API requests during KVM connection setup (KVM_TIMING)",
-			Buckets: []float64{0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2},
-		},
-		[]string{"endpoint"},
-	)
 )
 
 // RecordWebsocketUpgrade records the WebSocket upgrade duration metric.
@@ -164,11 +155,6 @@ func RecordConsentCodeWait(duration time.Duration, mode string) {
 	kvmConsentCodeWaitSeconds.WithLabelValues(mode).Observe(duration.Seconds())
 }
 
-// RecordAPIRequest records the API request duration metric.
-func RecordAPIRequest(duration time.Duration, endpoint string) {
-	kvmAPIRequestSeconds.WithLabelValues(endpoint).Observe(duration.Seconds())
-}
-
 // RecordDeviceLookup records the device lookup duration metric.
 func RecordDeviceLookup(duration time.Duration) {
 	kvmDeviceLookupSeconds.Observe(duration.Seconds())