feat: allow oveeridng nested runtime config with env

playground/nitro.config.ts

@@ -1 +1 @@
-export default defineNitroConfig({});
+export default defineNitroConfig({});

src/runtime/config.ts

@@ -68,10 +68,21 @@ function _applyEnv(obj: object, parentKey = "") {
     const subKey = parentKey ? `${parentKey}_${key}` : key;
     const envValue = _getEnv(subKey);
     if (_isObject(obj[key])) {
+      // Same as before
       if (_isObject(envValue)) {
-        obj[key] = { ...obj[key], ...(envValue as any) };
+        obj[key] = { ...obj[key], ...(envValue as object) };
+        _applyEnv(obj[key], subKey);
+      }
+      // If envValue is undefined
+      // Then proceed to nested properties
+      else if (envValue === undefined) {
+        _applyEnv(obj[key], subKey);
+      }
+      // If envValue is a primitive other than undefined
+      // Then set objValue and ignore the nested properties
+      else {
+        obj[key] = envValue ?? obj[key];
       }
-      _applyEnv(obj[key], subKey);
     } else {
       obj[key] = envValue ?? obj[key];
     }