move max_request_size from agent to server (#1145)

moves the config option for max request size up to the front end, adds the env
var for it there, adds a server test for it and removes it from agent. a
request is either gonna come through the lb (before grpc) or to the server, we
can handle limiting the request there at least now, which may be easier than
having multiple layers of request body checking. this aligns with not making
the agent as responsible for http behaviors (eventually, not at all once route
is fully deprecated).

api/server/server.go

@@ -122,6 +122,9 @@ const (
 	// EnvLBPlacementAlg is the algorithm to place fn calls to fn runners in lb.[0w
 	EnvLBPlacementAlg = "FN_PLACER"
 
+	// EnvMaxRequestSize sets the limit in bytes for any API request's length.
+	EnvMaxRequestSize = "FN_MAX_REQUEST_SIZE"
+
 	// DefaultLogLevel is info
 	DefaultLogLevel = "info"
 
@@ -249,6 +252,7 @@ func NewFromEnv(ctx context.Context, opts ...Option) *Server {
 	opts = append(opts, WithNodeCert(getEnv(EnvCert, "")))
 	opts = append(opts, WithNodeCertKey(getEnv(EnvCertKey, "")))
 	opts = append(opts, WithNodeCertAuthority(getEnv(EnvCertAuth, "")))
+	opts = append(opts, LimitRequestBody(int64(getEnvInt(EnvMaxRequestSize, 0))))
 
 	publicLBURL := getEnv(EnvPublicLoadBalancerURL, "")
 	if publicLBURL != "" {