A validated image reference, separate from its registry HTTP endpoint.
@type t() :: %Regc.Oci.Reference{ digest: String.t() | nil, original: String.t(), registry: String.t(), repository: String.t(), scheme: String.t(), tag: String.t() | nil }
@spec parse( String.t(), keyword() ) :: {:ok, t()} | {:error, Regc.Oci.Error.t()}
@spec pin(t(), String.t()) :: t()
@spec selector(t()) :: String.t()