New login screen needs more customisation

[craigs100]

Now the login screen is all css vars there isn't enough flexibility to create required branding. The following are problems:-

1. The Heading colour also changes the button background colour. Needs to be different.
2. There is no way to change the colour of the forgotten password link text.
3. When not using the "normal" background image, there is no way to replace the Umbraco logo with your own.
4. There is no way to change the background colour and padding around the login form.

As I brand every site's login, I consider the login screen to be part of the front end, not the back end. These missing facilities arose when trying to set a black background and a white logo. More or less trying to recreate the attached image but with the modern form elements. I found it impossible. I don't think it's unreasonable to be able to do this, but the current set up means the logo isn't available unless you set the background images first and have it in the new left hand box area. I understand you might be able to change the flex layout, but that still doesn't allow you to show a logo without a background image behind it.

I note that you can put a page-wide image behind it all, which is good, however I think at the moment it's a regression on creativity. Hopefully it can be fixed in fairly short order. Essentially just need access to "all" the bits, including form padding and border radii, and the ability to put a alpha controlled colour over the background image, to be able to mute it.