fix(api): CORS for connectRPC and grpc-web (#10227)

# Which Problems Are Solved

The CORS handler for the new connectRPC handlers was missing, leading to
unhandled preflight requests and a unusable api for browser based calls,
e.g. cross domain gRPC-web requests.

# How the Problems Are Solved

- Added the http CORS middleware to the connectRPC handlers.
- Added `Grpc-Timeout`, `Connect-Protocol-Version`,`Connect-Timeout-Ms`
to the default allowed headers (this improves also the old grpc-web
handling)
- Added `Grpc-Status`, `Grpc-Message`, `Grpc-Status-Details-Bin` to the
default exposed headers (this improves also the old grpc-web handling)

# Additional Changes

None

# Additional Context

noticed internally while testing other issues

internal/api/api.go

@@ -201,7 +201,7 @@ func (a *API) registerConnectServer(service server.ConnectServer) {
 		methodNames[i] = string(methods.Get(i).Name())
 	}
 	a.connectServices[prefix] = methodNames
-	a.RegisterHandlerPrefixes(handler, prefix)
+	a.RegisterHandlerPrefixes(http_mw.CORSInterceptor(handler), prefix)
 }
 
 // HandleFunc allows registering a [http.HandlerFunc] on an exact

internal/api/http/header.go

@@ -10,30 +10,36 @@ import (
 )
 
 const (
-	Authorization    = "authorization"
+	Authorization          = "authorization"
-	Accept           = "accept"
+	Accept                 = "accept"
-	AcceptLanguage   = "accept-language"
+	AcceptLanguage         = "accept-language"
-	CacheControl     = "cache-control"
+	CacheControl           = "cache-control"
-	ContentType      = "content-type"
+	ContentType            = "content-type"
-	ContentLength    = "content-length"
+	ContentLength          = "content-length"
-	ContentLocation  = "content-location"
+	ContentLocation        = "content-location"
-	Expires          = "expires"
+	Expires                = "expires"
-	Location         = "location"
+	Location               = "location"
-	Origin           = "origin"
+	Origin                 = "origin"
-	Pragma           = "pragma"
+	Pragma                 = "pragma"
-	UserAgentHeader  = "user-agent"
+	UserAgentHeader        = "user-agent"
-	ForwardedFor     = "x-forwarded-for"
+	ForwardedFor           = "x-forwarded-for"
-	ForwardedHost    = "x-forwarded-host"
+	ForwardedHost          = "x-forwarded-host"
-	ForwardedProto   = "x-forwarded-proto"
+	ForwardedProto         = "x-forwarded-proto"
-	Forwarded        = "forwarded"
+	Forwarded              = "forwarded"
-	ZitadelForwarded = "x-zitadel-forwarded"
+	ZitadelForwarded       = "x-zitadel-forwarded"
-	XUserAgent       = "x-user-agent"
+	XUserAgent             = "x-user-agent"
-	XGrpcWeb         = "x-grpc-web"
+	XGrpcWeb               = "x-grpc-web"
-	XRequestedWith   = "x-requested-with"
+	XRequestedWith         = "x-requested-with"
-	XRobotsTag       = "x-robots-tag"
+	XRobotsTag             = "x-robots-tag"
-	IfNoneMatch      = "If-None-Match"
+	IfNoneMatch            = "if-none-match"
-	LastModified     = "Last-Modified"
+	LastModified           = "last-modified"
-	Etag             = "Etag"
+	Etag                   = "etag"
+	GRPCTimeout            = "grpc-timeout"
+	ConnectProtocolVersion = "connect-protocol-version"
+	ConnectTimeoutMS       = "connect-timeout-ms"
+	GrpcStatus             = "grpc-status"
+	GrpcMessage            = "grpc-message"
+	GrpcStatusDetailsBin   = "grpc-status-details-bin"
 
 	ContentSecurityPolicy   = "content-security-policy"
 	XXSSProtection          = "x-xss-protection"

internal/api/http/middleware/cors_interceptor.go

@@ -21,6 +21,9 @@ var (
 			http_utils.XUserAgent,
 			http_utils.XGrpcWeb,
 			http_utils.XRequestedWith,
+			http_utils.ConnectProtocolVersion,
+			http_utils.ConnectTimeoutMS,
+			http_utils.GRPCTimeout,
 		},
 		AllowedMethods: []string{
 			http.MethodOptions,
@@ -34,6 +37,9 @@ var (
 		ExposedHeaders: []string{
 			http_utils.Location,
 			http_utils.ContentLength,
+			http_utils.GrpcStatus,
+			http_utils.GrpcMessage,
+			http_utils.GrpcStatusDetailsBin,
 		},
 		AllowOriginFunc: func(_ string) bool {
 			return true