[8.x] Add note to not use hasOne of many relation in PostgresSQL

[pushpak1300]

As mentioned in issue laravel/framework#37854.
and in the following comment laravel/framework#37362 (comment).
I noticed that Has One Of Many relationships is not working in PostgresSQL if we are using UUID as a primary key.

Regarding UUIDs, they are sortable by using (string) Str::orderedUuid() as your model UUIDs instead of the typical (string) Str::uuid().

I have used Str::orderedUuid() to generate the models primary key but still, this issue is there.
Until this issue get's resolved we should display the note on the website to save some debugging time for other users.

[taylorotwell]

Better for us to research and fix the issue.

[pushpak1300]

Sounds good @taylorotwell
I have created the example repository you can check and possibly try to reproduce the issue at your end.
laravel/framework#37854 (comment)