extendXxCollection() doesn't warn about extraneous properties

[minenwerfer]

The fix is simple:

export declare const extendUserCollection: <
  const TCollection extends {
    [P in Exclude<keyof Collection, "functions">]?: Partial<Collection[P]>;
  } & {
    functions?: {
      [F: string]: (
        payload: any,
        context: Context<(typeof user)["description"]>
      ) => unknown;
    };
  }
>(
- collection: TCollection
+ collection: Pick<TCollection, keyof Collection>
) => ExtendCollection<typeof user, TCollection>;

[minenwerfer]

Reopening this issue as the proposed fix crashed some existing applications.
We should revert back to the old form for now while a better solution doesn't appear.