Load user profile when SSH (#380)

This PR fixes issues with the terminal when
running netbird ssh to a remote agent.
Every session looks up a user and loads its
profile. If no user is found, the connection is rejected.
The default user is root.

util/common.go

@@ -1,5 +1,7 @@
 package util
 
+import "os"
+
 // SliceDiff returns the elements in slice `x` that are not in slice `y`
 func SliceDiff(x, y []string) []string {
 	mapY := make(map[string]struct{}, len(y))
@@ -14,3 +16,9 @@ func SliceDiff(x, y []string) []string {
 	}
 	return diff
 }
+
+// FileExists returns true if specified file exists
+func FileExists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}