Adds an edge between two vertices in the builder.

Validation

• Both vertices must exist in the builder.

@spec add_vertex({:ok, t()}, String.t(), (map() -> map()), keyword()) ::
  {:ok, t()} | {:error, String.t()}

Adds a vertex to the builder.

Validation

• The vertex must have a unique name.

@spec build(String.t()) :: {:ok, t()}

Initializes a new graph builder with the given name.

@spec finish({:ok, t()}) :: {:ok, String.t(), pid()} | {:error, String.t()}

Creates the graph using the builder's properties.