GM properties have shared backends

Hello!

I have a Chevrolet vehicle, and I've noticed that when logging into my Chevrolet account, the URL is in the format of `custlogin.gm.com/(stuff)`. However, the change password page is on `my.chevrolet.com/account`. This isn't an issue when first logging into an account as only gm.com is interacted with for login purposes. The issue occurs when a user attempts to change passwords. A password manager will then have two conflicting passwords, one for `custlogin.gm.com` and for `my.chevrolet.com`, and the old password for `custlogin.gm.com` will take priority in normal login attempts, which will fail.

The concern I have is how this interacts with other GM properties, such as Buick and GMC. Since I have only one GM vehicle, I don't believe I can test on other GM properties. In addition, what happens if a user owns multiple vehicles from different GM brands. For example, if someone owns both a GMC truck and a Chevrolet SUV, is there just one account used across all three domains (gm.com, chevrolet.com, and gmc.com), or is it two accounts used across three domains (chevrolet.com and gm.com, AND gmc.com and gm.com)?

The report names custlogin.gm.com, my.chevrolet.com, gm.com, and gmc.com; first verify whether these properties share one account and how password changes are handled. Done means documenting the confirmed relationship and any required password-manager resource update.

Written by the indexing model from the issue text.