Multiple source cities on send resources

[Kiskadee-dev]

Currently, the sendresource functionality requires users to specify source cities individually, which can be repetitive and cumbersome when dealing with multiple cities. To improve usability and efficiency I suggest enhancing this functionality to allow for the selection of multiple cities without the need for repetitive input.

Proposed Changes:

0. Cache the current resources so the next steps are faster. (The select cities should also have some sort of caching, ppl doesn't create/remove cities that often).
1. Source City Selection: Enable users to select multiple source cities simultaneously, eliminating the need for repetitive input.
2. Target City: Keep the option to choose the target city.
3. Show the available resources from the selected sources.
4. Select Resources: Allow users to choose the resources they want to send.
5. Resource Allocation: When more than one source city is selected, provide the option to either split the chosen resources evenly between them or specify a custom resource allocation ratio, otherwise keep the old behaviour to allow backwards compatibility.

Benefits:

• Streamlines the process of sending resources from multiple cities.
• Reduces user effort and potential errors caused by repetitive input.
• Offers flexibility with resource allocation when dealing with multiple source cities.

Use case:

• User Scenario: A user wants to send a significant quantity of wood and marble from several source cities to a single destination.
• Current Process: The user must repeatedly input the same destination for each source, leading to redundancy.
• Proposed Process: chooses multiple source cities, specifies the destination city once, then selects the amount of wood and marble and decides whether to distribute the resources evenly or customarily among the sources.