fix: validation (better #8456) (#8461)

* Revert "revert 484e023c0"

This reverts commit c03b70c949.

* also allow pure renote

* fix checks for pure renote

packages/backend/src/server/api/endpoints/pages/show.ts

@@ -26,12 +26,21 @@ export const meta = {
 
 export const paramDef = {
 	type: 'object',
-	properties: {
-		pageId: { type: 'string', format: 'misskey:id' },
-		name: { type: 'string' },
-		username: { type: 'string' },
-	},
-	required: [],
+	anyOf: [
+		{
+			properties: {
+				pageId: { type: 'string', format: 'misskey:id' },
+			},
+			required: ['pageId'],
+		},
+		{
+			properties: {
+				name: { type: 'string' },
+				username: { type: 'string' },
+			},
+			required: ['name', 'username'],
+		},
+	],
 } as const;
 
 // eslint-disable-next-line import/no-default-export