chore!: admin now takes a client side custom property and custom is server only (#5926)

packages/payload/src/globals/config/client.ts

@@ -12,7 +12,7 @@ import { createClientFieldConfigs } from '../../fields/config/client.js'
 
 export type ServerOnlyGlobalProperties = keyof Pick<
   SanitizedGlobalConfig,
-  'access' | 'admin' | 'endpoints' | 'fields' | 'hooks'
+  'access' | 'admin' | 'custom' | 'endpoints' | 'fields' | 'hooks'
 >
 export type ServerOnlyGlobalAdminProperties = keyof Pick<
   SanitizedGlobalConfig['admin'],
@@ -46,6 +46,7 @@ export const createClientGlobalConfig = ({
     'hooks',
     'access',
     'endpoints',
+    'custom',
     // `admin` is handled separately
   ]
 
@@ -55,12 +56,6 @@ export const createClientGlobalConfig = ({
     }
   })
 
-  if ('custom' in sanitized && sanitized.custom) {
-    if ('server' in sanitized.custom && sanitized.custom.server) {
-      delete sanitized.custom.server
-    }
-  }
-
   if ('admin' in sanitized) {
     sanitized.admin = { ...sanitized.admin }