Set x-inngest-expected-server-kind header (#37)

handler.go

@@ -219,6 +219,12 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	case http.MethodPut:
 		if err := h.register(w, r); err != nil {
 			h.Logger.Error("error registering functions", "error", err.Error())
+
+			w.WriteHeader(500)
+			w.Header().Set("Content-Type", "application/json")
+			_ = json.NewEncoder(w).Encode(map[string]string{
+				"message": err.Error(),
+			})
 		}
 		return
 	}
@@ -357,6 +363,15 @@ func (h *handler) register(w http.ResponseWriter, r *http.Request) error {
 		req.URL.RawQuery = qp.Encode()
 	}
 
+	// If the request specifies a server kind then include it as an expectation
+	// in the outgoing request
+	if r.Header.Get(HeaderKeyServerKind) != "" {
+		req.Header.Set(
+			HeaderKeyExpectedServerKind,
+			r.Header.Get(HeaderKeyServerKind),
+		)
+	}
+
 	key, err := hashedSigningKey([]byte(h.GetSigningKey()))
 	if err != nil {
 		return fmt.Errorf("error creating signing key: %w", err)

headers.go

@@ -6,14 +6,16 @@ import (
 )
 
 const (
-	HeaderKeyAuthorization = "Authorization"
-	HeaderKeyContentType   = "Content-Type"
-	HeaderKeyEnv           = "X-Inngest-Env"
-	HeaderKeyNoRetry       = "X-Inngest-No-Retry"
-	HeaderKeyRetryAfter    = "Retry-After"
-	HeaderKeySDK           = "X-Inngest-SDK"
-	HeaderKeySignature     = "X-Inngest-Signature"
-	HeaderKeyUserAgent     = "User-Agent"
+	HeaderKeyAuthorization      = "Authorization"
+	HeaderKeyContentType        = "Content-Type"
+	HeaderKeyEnv                = "X-Inngest-Env"
+	HeaderKeyExpectedServerKind = "X-Inngest-Expected-Server-Kind"
+	HeaderKeyNoRetry            = "X-Inngest-No-Retry"
+	HeaderKeyRetryAfter         = "Retry-After"
+	HeaderKeySDK                = "X-Inngest-SDK"
+	HeaderKeyServerKind         = "X-Inngest-Server-Kind"
+	HeaderKeySignature          = "X-Inngest-Signature"
+	HeaderKeyUserAgent          = "User-Agent"
 )
 
 var (