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/model/model.go

@@ -384,6 +384,13 @@ func (s *State) KeyByName(name string) *TSIGKey {
 	return nil
 }
 
+// ViewKeyPrefix starts the names of the TSIG keys Jarl gives views
+// (render/viewkeys.go); other keys can't use it.
+const ViewKeyPrefix = "jarl-view-"
+
+// ViewKeyName returns the name of a view's key.
+func ViewKeyName(view string) string { return ViewKeyPrefix + view }
+
 // NormalizeKeyName returns the canonical form of a key name: lowercase,
 // without a trailing dot.
 func NormalizeKeyName(name string) string {