[FR] Allow styling of `OnlineUnlockForm::OverlayComp`

We are using the OnlineUnlockForm class for authorisation. We can inherit from it and style it, but we are stuck with a white rectangle with a spinner while it waits for the server response.

OnlineUnlockForm::OverlayComp is a private class. Can we at least have the ability to set the colours. Ideally allow overriding of the paint/resize methods.

Iā€™m hoping to be able to avoid copying and pasting the whole thing into a new class :slight_smile: