allow users to opt out of deprecation warnings by setting flags to false (#12441)

* allow users to opt out of deprecation warnings by setting flags to false

* Create slow-birds-fetch.md

Author: brookslybrand

.changeset/slow-birds-fetch.md

@@ -0,0 +1,5 @@
+---
+"react-router": patch
+---
+
+Allow users to opt out of deprecation warnings by setting flags to false

packages/react-router/lib/deprecations.ts

@@ -22,7 +22,7 @@ export function logV6DeprecationWarnings(
   renderFuture: Partial<RenderFutureConfig> | undefined,
   routerFuture?: Omit<RouterFutureConfig, "v7_prependBasename">
 ) {
-  if (!renderFuture?.v7_startTransition) {
+  if (renderFuture?.v7_startTransition === undefined) {
     logDeprecation(
       "v7_startTransition",
       "React Router will begin wrapping state updates in `React.startTransition` in v7",
@@ -31,7 +31,7 @@ export function logV6DeprecationWarnings(
   }
 
   if (
-    !renderFuture?.v7_relativeSplatPath &&
+    renderFuture?.v7_relativeSplatPath === undefined &&
     (!routerFuture || !routerFuture.v7_relativeSplatPath)
   ) {
     logDeprecation(
@@ -42,31 +42,31 @@ export function logV6DeprecationWarnings(
   }
 
   if (routerFuture) {
-    if (!routerFuture.v7_fetcherPersist) {
+    if (routerFuture.v7_fetcherPersist === undefined) {
       logDeprecation(
         "v7_fetcherPersist",
         "The persistence behavior of fetchers is changing in v7",
         "https://reactrouter.com/v6/upgrading/future#v7_fetcherpersist"
       );
     }
 
-    if (!routerFuture.v7_normalizeFormMethod) {
+    if (routerFuture.v7_normalizeFormMethod === undefined) {
       logDeprecation(
         "v7_normalizeFormMethod",
         "Casing of `formMethod` fields is being normalized to uppercase in v7",
         "https://reactrouter.com/v6/upgrading/future#v7_normalizeformmethod"
       );
     }
 
-    if (!routerFuture.v7_partialHydration) {
+    if (routerFuture.v7_partialHydration === undefined) {
       logDeprecation(
         "v7_partialHydration",
         "`RouterProvider` hydration behavior is changing in v7",
         "https://reactrouter.com/v6/upgrading/future#v7_partialhydration"
       );
     }
 
-    if (!routerFuture.v7_skipActionErrorRevalidation) {
+    if (routerFuture.v7_skipActionErrorRevalidation === undefined) {
       logDeprecation(
         "v7_skipActionErrorRevalidation",
         "The revalidation behavior after 4xx/5xx `action` responses is changing in v7",