Add new node to exist assignment with the least change

[Khixinhxan]

What language and solver does this apply to?
Python 3.7
or-tools 7.4.7247
Mac Os system
Routing

Describe the problem you are trying to solve.
Current, I want to find solution for add new node to exist assignment was solved by model
Example:
I have 40 nodes and 20 vehicles, I using SolveWithParameters to solve.
First result I have 10 vehicles as 10 routes, cross 40 initial nodes.
Now, I have one new node, I want to add this new node to first result with the least change in the first result
But I re generate RoutingIndexManager, RoutingModel and use SolveWithParameters to solve then I will have new result, change more than 40 50 percents.

Describe the solution you'd like
I think two case to solve:

1. Add new node to new vehicle, I will have 11 vehicle as 11 routes.
2. I think search from first result, find the vehicle have free time, capacity of vehicle not full to add one new node, reset the ordered this route to optimize (min total time, min total distance, ...), so second result change only one vehicle.

Describe alternatives you've considered

Additional context
Add any other context or screenshots about the feature request here.

[Mizux]

• Add the new node in a disjunction so you can use the previous assignment as initial solution
  see: https://gist.github.com/Mizux/0bd1daadc4e64130b62492c942f163d5

• force all previous node to the vehicle in the previous assignment so they won't be moved to another vehicle aka

routing.VechicleVar(index_N).SetValue(vehicle_X)

• You can take a look at ApplyLock() method
  

  or-tools/ortools/constraint_solver/routing.h

  Lines 1043 to 1061 in fa84bc0

  	/// Applies a lock chain to the next search. 'locks' represents an ordered
  	/// vector of nodes representing a partial route which will be fixed during
  	/// the next search; it will constrain next variables such that:
  	/// next[locks[i]] == locks[i+1].
  	///
  	/// Returns the next variable at the end of the locked chain; this variable is
  	/// not locked. An assignment containing the locks can be obtained by calling
  	/// PreAssignment().
  	IntVar* ApplyLocks(const std::vector<int64>& locks);
  	/// Applies lock chains to all vehicles to the next search, such that locks[p]
  	/// is the lock chain for route p. Returns false if the locks do not contain
  	/// valid routes; expects that the routes do not contain the depots,
  	/// i.e. there are empty vectors in place of empty routes.
  	/// If close_routes is set to true, adds the end nodes to the route of each
  	/// vehicle and deactivates other nodes.
  	/// An assignment containing the locks can be obtained by calling
  	/// PreAssignment().
  	bool ApplyLocksToAllVehicles(const std::vector<std::vector<int64>>& locks,
  	bool close_routes);

  
  cons: since the lock force the nextVar the new node won't/can't be inserted in the middle of the chain...