Public read-only share link (no login / no OIDC) (#41) (#43)

Per-garden public read-only link: unauthenticated GET /api/v1/public/gardens/:token (no requireAuth, no OIDC), owner-only enable/rotate/disable, and a /g/$token page rendering GardenCanvas read-only. Review fixes: redact plant owner ids, Cache-Control: no-store, 400 on malformed body, shared resetTransient store action.

Closes #41.

Co-authored-by: Steve Dudenhoeffer <[email protected]>

internal/service/service.go

@@ -59,16 +59,25 @@ func formatTime(t time.Time) string { return t.UTC().Format(timeLayout) }
 // parseTime parses a canonical pansy timestamp.
 func parseTime(s string) (time.Time, error) { return time.Parse(timeLayout, s) }
 
-// newSessionToken returns a fresh URL-safe random bearer token (32 bytes of
-// entropy). The raw token goes in the cookie; only its hash is persisted.
-func newSessionToken() (string, error) {
-	b := make([]byte, 32)
+// randToken returns nBytes of cryptographic randomness as a URL-safe string.
+func randToken(nBytes int) (string, error) {
+	b := make([]byte, nBytes)
 	if _, err := rand.Read(b); err != nil {
-		return "", fmt.Errorf("service: generate session token: %w", err)
+		return "", fmt.Errorf("service: generate token: %w", err)
 	}
 	return base64.RawURLEncoding.EncodeToString(b), nil
 }
 
+// newSessionToken returns a fresh URL-safe random bearer token (32 bytes of
+// entropy). The raw token goes in the cookie; only its hash is persisted.
+func newSessionToken() (string, error) { return randToken(32) }
+
+// newPublicToken returns a fresh unguessable token for a garden's public share
+// link (18 bytes → 144 bits; a 24-char URL segment). Unlike a session token it's
+// stored raw (it must be shown back to the owner to copy) and grants only
+// read-only access to one garden.
+func newPublicToken() (string, error) { return randToken(18) }
+
 // hashToken maps a raw bearer token to the hex sha256 stored as the session's
 // primary key.
 func hashToken(raw string) string {