Allow parachains to send messages (#274)

* Slots module

* Integrate slots

* More drafting

* Minor updates

* Update parachains to use trati

* More build fixes

* Full code now compiles

* Add renew bid function

* Implement calculate_winner

* Warning remove

* Update gitignore

* Test framework

* Tests

* Further testing

* More tests, new parameterisation.

* Fix and new test

* Thread-safe tests

* Test off-boarding and a fix.

* Test onboarding

* Allow late onboarding.

* Another test and fix

* Avoid println in nostd

* Compact representation of paraids

* Introduce documentation.

* Introduce events.

* Additional test and fix

* Additional test

* Tidy up line lengths.

* Remove printlns

* Use later substrate utils.

* Allow parachains to send messages.

* Fix build/test

* Make slots work with latest substrate

* Update runtime/src/slot_range.rs

Co-Authored-By: Robert Habermeier <rphmeier@gmail.com>

* Update runtime/src/slots.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update runtime/src/slots.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Polish logic

* Rewind to earlier substrate master

* Remove dead code.

* Fix build

* Update substrate ref to master

* Update to new inherent digests API

* address grumbles

* fix

* Fix a warning.

* Reworded a comment.

* Check that receipt matches expectations

* Add test for final checks

* Split out queuing logic.

* Test final piece of queuing logic

* Fix up docs.

* More docs fixes

polkadot/parachain/src/lib.rs

@@ -197,3 +197,37 @@ pub struct MessageRef<'a> {
 	/// Underlying data of the message.
 	pub data: &'a [u8],
 }
+
+/// Which origin a parachain's message to the relay chain should be dispatched from.
+#[derive(Clone, PartialEq, Eq, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug))]
+#[repr(u8)]
+pub enum ParachainDispatchOrigin {
+	/// As a simple `Origin::Signed`, using `ParaId::account_id` as its value. This is good when
+	/// interacting with standard modules such as `balances`.
+	Signed,
+	/// As the special `Origin::Parachain(ParaId)`. This is good when interacting with parachain-
+	/// aware modules which need to succinctly verify that the origin is a parachain.
+	Parachain,
+}
+
+impl core::convert::TryFrom<u8> for ParachainDispatchOrigin {
+	type Error = ();
+	fn try_from(x: u8) -> core::result::Result<ParachainDispatchOrigin, ()> {
+		const SIGNED: u8 = ParachainDispatchOrigin::Signed as u8;
+		const PARACHAIN: u8 = ParachainDispatchOrigin::Parachain as u8;
+		Ok(match x {
+			SIGNED => ParachainDispatchOrigin::Signed,
+			PARACHAIN => ParachainDispatchOrigin::Parachain,
+			_ => return Err(()),
+		})
+	}
+}
+
+/// A reference to an upward message.
+pub struct UpwardMessageRef<'a> {
+	/// The origin type.
+	pub origin: ParachainDispatchOrigin,
+	/// Underlying data of the message.
+	pub data: &'a [u8],
+}