Document smb_id for synced folders

[efussi]

When using the id option documented here like this

config.vm.synced_folder "C:/projects", "/projects", type: "smb", id: "projects", smb_username: ENV['SMB_USERNAME'], smb_password: ENV['SMB_PASSWORD'], mount_options: ["vers=3.0"]

I got this in my VM:

$ mount
//172.22.32.1/vgt-69a3aff238e79c45ffd1cd0472ccc0ad-35a2864c314e4367eb1684bfe126a967 on /projects type cifs (rw,relatime,vers=3.0,...
: 

Changing id to smb_id like this

config.vm.synced_folder "C:/projects", "/projects", type: "smb", smb_id: "projects", smb_username: ENV['SMB_USERNAME'], smb_password: ENV['SMB_PASSWORD'], mount_options: ["vers=3.0"]

yields the desired result:

$ mount
//172.22.32.1/projects on /projects type cifs (rw,relatime,vers=3.0,...
: 

[hashicorp-cla-app]

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