feat: add flag to disable template insights (#20940)

Closes #20399 

To summarize the original commit messages:

- Do not log stats to the database.
- Return errors on the insight endpoints.
- Update the frontend to show those errors.
- Also fixes an issue with getting the user status count via codersdk,
since I added a test to ensure it was not disabled by this flag and it
was sending the wrong payload.

coderd/agentapi/stats_test.go

@@ -28,7 +28,7 @@ import (
 	"github.com/coder/coder/v2/testutil"
 )
 
-func TestUpdateStates(t *testing.T) {
+func TestUpdateStats(t *testing.T) {
 	t.Parallel()
 
 	var (
@@ -542,6 +542,135 @@ func TestUpdateStates(t *testing.T) {
 		}
 		require.True(t, updateAgentMetricsFnCalled)
 	})
+
+	t.Run("DropStats", func(t *testing.T) {
+		t.Parallel()
+
+		var (
+			now = dbtime.Now()
+			dbM = dbmock.NewMockStore(gomock.NewController(t))
+			ps  = pubsub.NewInMemory()
+
+			templateScheduleStore = schedule.MockTemplateScheduleStore{
+				GetFn: func(context.Context, database.Store, uuid.UUID) (schedule.TemplateScheduleOptions, error) {
+					panic("should not be called")
+				},
+				SetFn: func(context.Context, database.Store, database.Template, schedule.TemplateScheduleOptions) (database.Template, error) {
+					panic("not implemented")
+				},
+			}
+			updateAgentMetricsFnCalled = false
+			tickCh                     = make(chan time.Time)
+			flushCh                    = make(chan int, 1)
+			wut                        = workspacestats.NewTracker(dbM,
+				workspacestats.TrackerWithTickFlush(tickCh, flushCh),
+			)
+
+			req = &agentproto.UpdateStatsRequest{
+				Stats: &agentproto.Stats{
+					ConnectionsByProto: map[string]int64{
+						"tcp":  1,
+						"dean": 2,
+					},
+					ConnectionCount:             3,
+					ConnectionMedianLatencyMs:   23,
+					RxPackets:                   120,
+					RxBytes:                     1000,
+					TxPackets:                   130,
+					TxBytes:                     2000,
+					SessionCountVscode:          1,
+					SessionCountJetbrains:       2,
+					SessionCountReconnectingPty: 3,
+					SessionCountSsh:             4,
+					Metrics: []*agentproto.Stats_Metric{
+						{
+							Name:  "awesome metric",
+							Value: 42,
+						},
+						{
+							Name:  "uncool metric",
+							Value: 0,
+						},
+					},
+				},
+			}
+		)
+		api := agentapi.StatsAPI{
+			AgentFn: func(context.Context) (database.WorkspaceAgent, error) {
+				return agent, nil
+			},
+			Workspace: &workspaceAsCacheFields,
+			Database:  dbM,
+			StatsReporter: workspacestats.NewReporter(workspacestats.ReporterOptions{
+				Database:              dbM,
+				Pubsub:                ps,
+				StatsBatcher:          nil, // Should not be called.
+				UsageTracker:          wut,
+				TemplateScheduleStore: templateScheduleStorePtr(templateScheduleStore),
+				UpdateAgentMetricsFn: func(ctx context.Context, labels prometheusmetrics.AgentMetricLabels, metrics []*agentproto.Stats_Metric) {
+					updateAgentMetricsFnCalled = true
+					assert.Equal(t, prometheusmetrics.AgentMetricLabels{
+						Username:      user.Username,
+						WorkspaceName: workspace.Name,
+						AgentName:     agent.Name,
+						TemplateName:  template.Name,
+					}, labels)
+					assert.Equal(t, req.Stats.Metrics, metrics)
+				},
+				DisableDatabaseInserts: true,
+			}),
+			AgentStatsRefreshInterval: 10 * time.Second,
+			TimeNowFn: func() time.Time {
+				return now
+			},
+		}
+		defer wut.Close()
+
+		// We expect an activity bump because ConnectionCount > 0.
+		dbM.EXPECT().ActivityBumpWorkspace(gomock.Any(), database.ActivityBumpWorkspaceParams{
+			WorkspaceID:   workspace.ID,
+			NextAutostart: time.Time{}.UTC(),
+		}).Return(nil)
+
+		// Workspace last used at gets bumped.
+		dbM.EXPECT().BatchUpdateWorkspaceLastUsedAt(gomock.Any(), database.BatchUpdateWorkspaceLastUsedAtParams{
+			IDs:        []uuid.UUID{workspace.ID},
+			LastUsedAt: now,
+		}).Return(nil)
+
+		// Ensure that pubsub notifications are sent.
+		notifyDescription := make(chan struct{})
+		ps.SubscribeWithErr(wspubsub.WorkspaceEventChannel(workspace.OwnerID),
+			wspubsub.HandleWorkspaceEvent(
+				func(_ context.Context, e wspubsub.WorkspaceEvent, err error) {
+					if err != nil {
+						return
+					}
+					if e.Kind == wspubsub.WorkspaceEventKindStatsUpdate && e.WorkspaceID == workspace.ID {
+						go func() {
+							notifyDescription <- struct{}{}
+						}()
+					}
+				}))
+
+		resp, err := api.UpdateStats(context.Background(), req)
+		require.NoError(t, err)
+		require.Equal(t, &agentproto.UpdateStatsResponse{
+			ReportInterval: durationpb.New(10 * time.Second),
+		}, resp)
+
+		tickCh <- now
+		count := <-flushCh
+		require.Equal(t, 1, count, "expected one flush with one id")
+
+		ctx := testutil.Context(t, testutil.WaitShort)
+		select {
+		case <-ctx.Done():
+			t.Error("timed out while waiting for pubsub notification")
+		case <-notifyDescription:
+		}
+		require.True(t, updateAgentMetricsFnCalled)
+	})
 }
 
 func templateScheduleStorePtr(store schedule.TemplateScheduleStore) *atomic.Pointer[schedule.TemplateScheduleStore] {