Add Multi-Samba User Mode

[HanLiQL]

When using samba, you may need to use different samba accounts to share different content.
If you run many docker container instances, it will make management more complicated.
I think it is not appropriate to start multiple container instances just because there are multiple accounts for a service.
So I modified the entrypoint script to introduce a multi-account mode.
Users can initialize multiple samba accounts and groups simultaneously by mounting configuration files, allowing for better customization of samba sharing policies.
This patch is compatible with previous versions, and existing configuration files do not need to be modified for existing users.

[xfl12345]

#12

[kroese]

This pull completely broke the single-user mode, because the pdbedit and smbpasswd dont expect the config file to be /etc/samba/smb.tmp.

Next time when adding new functionality, please be careful not to break the default mode because I merged it assuming you tested it.

[HanLiQL]

Thank you for pointing out my mistake and for fixing the code. I apologize for not testing all the possible scenarios.