Limit GUI process execution to one per UID (#2267)

replaces PID with checking process name and path and UID checks

client/ui/process.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/shirou/gopsutil/v3/process"
+)
+
+func isAnotherProcessRunning() (bool, error) {
+	processes, err := process.Processes()
+	if err != nil {
+		return false, err
+	}
+
+	pid := os.Getpid()
+	processName := strings.ToLower(filepath.Base(os.Args[0]))
+
+	for _, p := range processes {
+		if int(p.Pid) == pid {
+			continue
+		}
+
+		runningProcessPath, err := p.Exe()
+		// most errors are related to short-lived processes
+		if err != nil {
+			continue
+		}
+
+		if strings.Contains(strings.ToLower(runningProcessPath), processName) && isProcessOwnedByCurrentUser(p) {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}