Introduce DatagramOptions

[sjlgasnier]

Aims at closing #9

I wrote 2 new doctests for the asynchronous module, but I had to set the root options.rs file to public in order to use DatagramOptions.
Is it an issue ?

Feel free to tear those doctests if so.

[altonen]

Ty! Left a few documentation nits.

You also need to re-export DatagramOptions in src/lib.rs, i.e., add DatagramOptions to pub use options::{...}

[altonen]

Suggested change

	#[derive(Default)]
	pub struct DatagramOptions {
	/// Overrides the source port
	pub from_port: u16,
	/// Overrides the destination port
	pub to_port: u16,
	/// Overrides the I2P protocol used
	///
	/// Only for RAW/Anonymous sessions
	pub protocol: u8,
	/// Overrides the crypto_tags_to_send I2CP option
	pub send_tags: usize,
	/// Overrides the crypto_low_tag_threshold I2CP option
	pub tag_threshold: usize,
	/// Overrides the should_bundle_reply_info I2CP option
	pub send_leaseset: bool,
	}
	/// Datagram options.
	#[derive(Default)]
	pub struct DatagramOptions {
	/// Overrides the source port.
	///
	/// Defaults to `0`.
	pub from_port: u16,
	/// Overrides the destination port.
	///
	/// Defaults to `0`.
	pub to_port: u16,
	/// Overrides the I2P protocol used.
	///
	/// Only for RAW/Anonymous sessions.
	///
	/// Defaults to `18`.
	pub protocol: u8,
	/// Overrides the [`SessionOptions::crypto_tags_to_send`] I2CP option.
	///
	/// Defaults to `0`.
	pub send_tags: usize,
	/// Overrides the [`SessionOptions::crypto_low_tag_threshold`] I2CP option.
	///
	/// Defaults to `0`.
	pub tag_threshold: usize,
	/// Overrides the [`SessionOptions::should_bundle_reply_info`] I2CP option.
	///
	/// Defaults to `true`.
	pub send_lease_set: bool,
	}

[altonen]

Suggested change

	options.send_leaseset,
	options.send_lease_set,

[altonen]

Suggested change

	options.send_leaseset,
	options.send_lease_set,

[altonen]

Suggested change

	options.send_leaseset,
	options.send_lease_set,

[altonen]

Suggested change

	options.send_leaseset,
	options.send_lease_set,