Allow modules to validate transaction, second attempt (#2463)

* first impl

* rename origin::inherent to none

* fix

* fix

* Apply suggestions from code review

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* comment

* better error

* doc

* (add unsigned module 🤦)

* doc

* fix

* implement for node-template as well

* add validated unsigned to executor

* fix

* fix

* bump version

* testing xt

* remove extraneous logic

* licence

* impl test

substrate/srml/system/src/lib.rs

@@ -233,15 +233,17 @@ pub enum RawOrigin<AccountId> {
 	Root,
 	/// It is signed by some public key and we provide the `AccountId`.
 	Signed(AccountId),
-	/// It is signed by nobody but included and agreed upon by the validators anyway: it's "inherently" true.
-	Inherent,
+	/// It is signed by nobody, can be either:
+	/// * included and agreed upon by the validators anyway,
+	/// * or unsigned transaction validated by a module.
+	None,
 }
 
 impl<AccountId> From<Option<AccountId>> for RawOrigin<AccountId> {
 	fn from(s: Option<AccountId>) -> RawOrigin<AccountId> {
 		match s {
 			Some(who) => RawOrigin::Signed(who),
-			None => RawOrigin::Inherent,
+			None => RawOrigin::None,
 		}
 	}
 }
@@ -363,12 +365,12 @@ pub fn ensure_root<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), &'stati
 }
 
 /// Ensure that the origin `o` represents an unsigned extrinsic. Returns `Ok` or an `Err` otherwise.
-pub fn ensure_inherent<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), &'static str>
+pub fn ensure_none<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), &'static str>
 	where OuterOrigin: Into<Option<RawOrigin<AccountId>>>
 {
 	match o.into() {
-		Some(RawOrigin::Inherent) => Ok(()),
-		_ => Err("bad origin: expected to be an inherent origin"),
+		Some(RawOrigin::None) => Ok(()),
+		_ => Err("bad origin: expected to be no origin"),
 	}
 }