Add guest user clarification

doc/user/permissions.md

@@ -233,6 +233,16 @@ nested groups if you have membership in one of its parents.
 To learn more, read through the documentation on
 [subgroups memberships](group/subgroups/index.md#membership).
+## Guest User
+
+There is no specific way to assign guest user role. Once a user is created and 
+assigned to a project with a role as `Guest` user, this user will be considered 
+a guest user by GitLab and will not take up the license. If this user will be 
+assigned a higher role to any of the projects and groups then this user will 
+take a license seat. If a user creates a project this user becomes a maintainer, 
+therefore, takes up a license seat as well, in order to prevent this you have to 
+go and edit user profile and mark the user as External.
+
 ## External users permissions
 In cases where it is desired that a user has access only to some internal or