db, state: keep the ephemeral flag a node was created with

The flag moves from the key to the node, so a login with another key no
longer changes it. A user claiming a tagged node still clears it. v1
nodes carry the flag.

hscontrol/api/v1/nodes.go

@@ -50,6 +50,7 @@ type Node struct {
 	RegisterMethod  string          `enum:"REGISTER_METHOD_UNSPECIFIED,REGISTER_METHOD_AUTH_KEY,REGISTER_METHOD_CLI,REGISTER_METHOD_OIDC" json:"registerMethod"`
 	GivenName       string          `json:"givenName"`
 	Online          bool            `json:"online"`
+	Ephemeral       bool            `json:"ephemeral"`
 	ApprovedRoutes  []string        `json:"approvedRoutes"                                                                                nullable:"false"`
 	AvailableRoutes []string        `json:"availableRoutes"                                                                               nullable:"false"`
 	SubnetRoutes    []string        `json:"subnetRoutes"                                                                                  nullable:"false"`
@@ -600,6 +601,7 @@ func nodeFromView(view types.NodeView) Node {
 		RegisterMethod:  registerMethodEnum(view.RegisterMethod()),
 		GivenName:       view.GivenName(),
 		Online:          view.IsOnline().Valid() && view.IsOnline().Get(),
+		Ephemeral:       view.IsEphemeral(),
 		ApprovedRoutes:  nonNilStrings(util.PrefixesToString(view.ApprovedRoutes().AsSlice())),
 		AvailableRoutes: nonNilStrings(util.PrefixesToString(view.AnnouncedRoutes())),
 		SubnetRoutes:    []string{},