transition: Node: Update transferable nodes when node(s) are deleted

[kaligrafy]

we should update only the affected nodes (the modified ones + the nodes around them)

[tahini]

Where are the transferrable nodes located? In DB and/or in cache?

[kaligrafy]

Only in cache

[tahini]

I moved the Node class to the transition-common workspace. I'll work on this with TDD, writing the unit tests for it first.

[kaligrafy]

not urgent for first formation though, moving to 0.2.3

[tahini]

For the record, transferable nodes are updated when a single node is edited/added (with PR chairemobilite/transition-legacy#904, when a node changes position, previously transferable nodes now inaccessible are updated as well).

What is left is to update the previously transferable nodes when deleting potentially multiple nodes.

[tahini]

Now that those nodes are in the database, the content of the database will automatically delete all delete transferable nodes. What remains is to sync the cache when that happens.