Document content delta for streaming responses.
@type t() :: %Gemini.Types.Interactions.DeltaDocumentDelta{ data: String.t() | nil, mime_type: String.t() | nil, type: String.t(), uri: String.t() | nil }
@spec from_api(map() | nil) :: t() | nil
@spec to_api(t() | nil) :: map() | nil