CRDT: State-based LWW-Element Graph

State-based LWW-Element Graph with test cases.

The graph allows:

• Add a vertex/edge.
• Remove a vertex/edge.
• Check if a vertex is in the graph.
• Query for all vertices connected to a vertex.
• Find any path between two vertices.
• Merge with concurrent changes from other graph/replica.

References

• https://github.com/pfrazee/crdt_notes
• https://en.wikipedia.org/wiki/Conflict-free_replicated_data_type
• https://hal.inria.fr/inria-00555588/PDF/techreport.pdf