[management] Ensure SessionStartedAt has a default value (#6211)

* [management] Ensure SessionStartedAt has a default value

Avoid null values for the new column

* [management] Add PeerStatus with LastSeen in peer_test

* [management] Add migration for PeerStatusSessionStartedAt default value

* [management] Add PeerStatus with LastSeen in migration tests

management/server/migration/migration_test.go

@@ -198,7 +198,11 @@ func TestMigrateNetIPFieldFromBlobToJSON_WithJSONData(t *testing.T) {
 	require.NoError(t, err, "Failed to insert account")
 
 	account.PeersG = []nbpeer.Peer{
-		{AccountID: "1234", Location: nbpeer.Location{ConnectionIP: net.IP{10, 0, 0, 1}}},
+		{
+			AccountID: "1234",
+			Location:  nbpeer.Location{ConnectionIP: net.IP{10, 0, 0, 1}},
+			Status:    &nbpeer.PeerStatus{LastSeen: time.Now()},
+		},
 	}
 
 	err = db.Save(account).Error

management/server/peer/peer.go

@@ -86,7 +86,7 @@ type PeerStatus struct { //nolint:revive
 	// active session". Integer nanoseconds are used so equality is
 	// precision-safe across drivers, and so the predicates compose to a
 	// single bigint comparison.
-	SessionStartedAt int64
+	SessionStartedAt int64 `gorm:"not null;default:0"`
 	// Connected indicates whether peer is connected to the management service or not
 	Connected bool
 	// LoginExpired

management/server/peer_test.go

@@ -2218,6 +2218,9 @@ func Test_IsUniqueConstraintError(t *testing.T) {
 		ID:        "test-peer-id",
 		AccountID: "bf1c8084-ba50-4ce7-9439-34653001fc3b",
 		DNSLabel:  "test-peer-dns-label",
+		Status: &nbpeer.PeerStatus{
+			LastSeen: time.Now(),
+		},
 	}
 
 	for _, tt := range tests {

management/server/store/store.go

@@ -471,6 +471,9 @@ func getMigrationsPreAuto(ctx context.Context) []migrationFunc {
 		func(db *gorm.DB) error {
 			return migration.MigrateNewField[types.User](ctx, db, "email", "")
 		},
+		func(db *gorm.DB) error {
+			return migration.MigrateNewField[nbpeer.Peer](ctx, db, "peer_status_session_started_at", int64(0))
+		},
 		func(db *gorm.DB) error {
 			return migration.RemoveDuplicatePeerKeys(ctx, db)
 		},