Give every view a TSIG key that selects it

Each view's match-clients starts with "key jarl-view-NAME" (after
"!key" for the views listed after it), so a query signed with a view's
key lands in that view from any address. The secrets are derived from a
random seed in Jarl's database. The delegation check signs its queries
to this server's own addresses with the key of the zone's view: before,
they got whichever view matched the server's address, usually internal.
jarl view key / GET /views/{id}/key show a key for dig -k (tsig:write,
audited). jarl-view- key names are reserved; the importer drops view
keys from a configuration Jarl wrote.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/engine/engine.go

@@ -75,6 +75,9 @@ type Engine struct {
 	Limits BlocklistLimits
 
 	namedCheck namedCheck // named-checkconf on the running configuration (namedwarn.go)
+
+	seedMu sync.Mutex
+	seed   []byte // the view keys' seed (viewkeys.go)
 }
 
 // New creates an engine.
@@ -437,7 +440,7 @@ func (e *Engine) makePlan(ctx context.Context, base, work *model.State, user str
 		pl.introduced = append(pl.introduced, problems...)
 		return pl, nil
 	}
-	pl.out = render.Render(work, e.cfg.Paths, e.cfg.Extras)
+	pl.out = render.Render(work, e.cfg.Paths, e.extras(ctx))
 	deployed, err := e.store.DeployedFiles(ctx)
 	if err != nil {
 		return nil, err
@@ -473,7 +476,7 @@ func (e *Engine) makePlan(ctx context.Context, base, work *model.State, user str
 	pl.diff = diff.String()
 
 	// Which zones named must reload, and which serials to verify.
-	baseOut := render.Render(base, e.cfg.Paths, e.cfg.Extras)
+	baseOut := render.Render(base, e.cfg.Paths, e.extras(ctx))
 	changedPaths := map[string]bool{}
 	for _, f := range pl.changed {
 		changedPaths[f.Path] = true
@@ -529,7 +532,7 @@ func (e *Engine) stagingCheck(ctx context.Context, pl *plan) error {
 	}
 	defer os.RemoveAll(dir)
 	sp := render.Paths{ConfigDir: filepath.Join(dir, "config"), ZoneDir: filepath.Join(dir, "zones"), CacheDir: filepath.Join(dir, "cache")}
-	sout := render.Render(pl.work, sp, e.cfg.Extras)
+	sout := render.Render(pl.work, sp, e.extras(ctx))
 	for _, d := range sout.Dirs {
 		if err := os.MkdirAll(d, 0o750); err != nil {
 			return err