Adds a node or nodes to an existing cluster identified by cluster_id

iex> c = Cluster.new
iex> n = Node.new
iex> Cluster.add(c.id, n)

Deletes the cluster with the provided cluster_id.

iex> Cluster.delete(1)

Find the cluster in the graph that has the provided cluster_id.

Returns the cluster, or nil if it is not found.

iex> c = Cluster.new
iex> Cluster.find(c.id) #=> returns `c`

Create a new cluster.

The cluster is empty by default, but can be provided with nodes already part of it.

iex> n = Node.new
iex> n2 = Node.new
iex> Cluster.new # or
iex> Cluster.new(n) # or
iex> Cluster.new([n, n2])

Removes a node or nodes from an existing cluster identified by cluster_id

iex> n = Node.new
iex> c = Cluster.new(n)
iex> Cluster.remove(c.id, n)