Use useradd on Alpine when user ID is large

[DenisRumyantsev]

Description: The adduser command can be used in Alpine by default without installing any additional packages. Therefore, this command has a higher priority. However, it does not work if the user ID is greater than 256000. In this case, we should install the additional shadow package and use the useradd command instead.

The shadow package will be used in the following cases:

• if this package is preinstalled in the container;
• if user ID is outside the range of the adduser command.

Related issue

[KonstantinTyukalov]

@DenisRumyantsev can we just always use the shadow package? Does it have some side effects?

[DenisRumyantsev]

@KonstantinTyukalov I suggest we can use the shadow package always when it is already installed in the container, and don't use it if it is not necessary and it is not installed yet.