Initial commit: Luminary AI Gateway

OpenAI-compatible AI gateway with Vue admin UI, multi-provider egress,
ingress key governance, monitoring, and security controls.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/gateway/upstream.go

@@ -0,0 +1,43 @@
+package gateway
+
+import "net/http"
+
+// retryableUpstreamStatus reports HTTP codes that should trigger retry / failover.
+func retryableUpstreamStatus(code int) bool {
+	switch code {
+	case http.StatusTooManyRequests,
+		http.StatusRequestTimeout,
+		http.StatusBadGateway,
+		http.StatusServiceUnavailable,
+		http.StatusGatewayTimeout:
+		return true
+	default:
+		return code >= 500
+	}
+}
+
+// tryNextKeyOnUpstreamStatus reports auth/rate errors where another provider key may work.
+func tryNextKeyOnUpstreamStatus(code int) bool {
+	switch code {
+	case http.StatusUnauthorized,
+		http.StatusForbidden,
+		http.StatusTooManyRequests,
+		http.StatusPaymentRequired:
+		return true
+	default:
+		return retryableUpstreamStatus(code)
+	}
+}
+
+// passThroughUpstreamStatus reports client errors that should be returned as-is.
+func passThroughUpstreamStatus(code int) bool {
+	switch code {
+	case http.StatusBadRequest,
+		http.StatusNotFound,
+		http.StatusUnprocessableEntity,
+		http.StatusUnsupportedMediaType:
+		return true
+	default:
+		return false
+	}
+}