resolve issues with missing user in containers

This change resolves an issue in container where the user id is not found.

This will create a passwd file with a single line that is for the container user using the uid and gid of the pterodactyl user.

As an added security benefit this would also stop users being able to just use `/bin/bash` as it sets the users terminal to nologin by default and is configurable

example passwd file contents  
`container❌999:999::/home/container:/usr/sbin/nologin`

config/config.go

@@ -168,6 +168,8 @@ type SystemConfiguration struct {
 
 		Uid int `yaml:"uid"`
 		Gid int `yaml:"gid"`
+
+		Login bool `yaml:"login"`
 	} `yaml:"user"`
 
 	// The amount of time in seconds that can elapse before a server's disk space calculation is
@@ -526,6 +528,24 @@ func ConfigureDirectories() error {
 		return err
 	}
 
+	log.WithField("filepath", "/etc/pterodactyl//passwd").Debug("ensuring passwd file exists")
+	if passwd, err := os.Create("/etc/pterodactyl/passwd"); err != nil {
+		return err
+	} else {
+		shell := "/usr/sbin/nologin"
+		if _config.System.User.Login {
+			shell = "/bin/sh"
+		}
+
+		// the WriteFile method returns an error if unsuccessful
+		err := os.WriteFile(passwd.Name(), []byte(fmt.Sprintf("container:x:%d:%d::/home/container:%s", _config.System.User.Uid, _config.System.User.Gid, shell)), 0777)
+		// handle this error
+		if err != nil {
+			// print it out
+			fmt.Println(err)
+		}
+	}
+
 	// There are a non-trivial number of users out there whose data directories are actually a
 	// symlink to another location on the disk. If we do not resolve that final destination at this
 	// point things will appear to work, but endless errors will be encountered when we try to

server/mounts.go

@@ -27,6 +27,12 @@ func (s *Server) Mounts() []environment.Mount {
 			Source:   s.Filesystem().Path(),
 			ReadOnly: false,
 		},
+		{
+			Default:  true,
+			Target:   "/etc/passwd",
+			Source:   "/etc/pterodactyl/passwd",
+			ReadOnly: true,
+		},
 	}
 
 	// Also include any of this server's custom mounts when returning them.