Several tweaks needed for Governance 2.0 (#11124)

* Add stepped curve for referenda

* Treasury SpendOrigin

* Add tests

* Better Origin Or-gating

* Reciprocal curve

* Tests for reciprical and rounding in PerThings

* Tweaks and new quad curve

* Const derivation of reciprocal curve parameters

* Remove some unneeded code

* Actually useful linear curve

* Fixes

* Provisional curves

* Rejig 'turnout' as 'support'

* Use TypedGet

* Fixes

* Enable curve's ceil to be configured

* Formatting

* Fixes

* Fixes

* Fixes

* Remove EnsureOneOf

* Fixes

* Fixes

* Fixes

* Formatting

* Fixes

* Update frame/support/src/traits/dispatch.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Grumbles

* Formatting

* Fixes

* APIs of VoteTally should include class

* Fixes

* Fix overlay prefix removal result

* Second part of the overlay prefix removal fix.

* Formatting

* Fixes

* Add some tests and make clear rounding algo

* Fixes

* Formatting

* Revert questionable fix

* Introduce test for kill_prefix

* Fixes

* Formatting

* Fixes

* Fix possible overflow

* Docs

* Add benchmark test

* Formatting

* Update frame/referenda/src/types.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* Docs

* Fixes

* Use latest API in tests

* Formatting

* Whitespace

* Use latest API in tests

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

substrate/frame/treasury/src/lib.rs

@@ -198,6 +198,11 @@ pub mod pallet {
 		/// NOTE: This parameter is also used within the Bounties Pallet extension if enabled.
 		#[pallet::constant]
 		type MaxApprovals: Get<u32>;
+
+		/// The origin required for approving spends from the treasury outside of the proposal
+		/// process. The `Success` value is the maximum amount that this origin is allowed to
+		/// spend at a time.
+		type SpendOrigin: EnsureOrigin<Self::Origin, Success = BalanceOf<Self, I>>;
 	}
 
 	/// Number of proposals that have been made.
@@ -275,6 +280,12 @@ pub mod pallet {
 		Rollover { rollover_balance: BalanceOf<T, I> },
 		/// Some funds have been deposited.
 		Deposit { value: BalanceOf<T, I> },
+		/// A new spend proposal has been approved.
+		SpendApproved {
+			proposal_index: ProposalIndex,
+			amount: BalanceOf<T, I>,
+			beneficiary: T::AccountId,
+		},
 	}
 
 	/// Error for the treasury pallet.
@@ -286,6 +297,9 @@ pub mod pallet {
 		InvalidIndex,
 		/// Too many approvals in the queue.
 		TooManyApprovals,
+		/// The spend origin is valid but the amount it is allowed to spend is lower than the
+		/// amount to be spent.
+		InsufficientPermission,
 		/// Proposal has not been approved.
 		ProposalNotApproved,
 	}
@@ -393,6 +407,40 @@ pub mod pallet {
 			Ok(())
 		}
 
+		/// Propose and approve a spend of treasury funds.
+		///
+		/// - `origin`: Must be `SpendOrigin` with the `Success` value being at least `amount`.
+		/// - `amount`: The amount to be transferred from the treasury to the `beneficiary`.
+		/// - `beneficiary`: The destination account for the transfer.
+		///
+		/// NOTE: For record-keeping purposes, the proposer is deemed to be equivalent to the
+		/// beneficiary.
+		#[pallet::weight(T::WeightInfo::spend())]
+		pub fn spend(
+			origin: OriginFor<T>,
+			#[pallet::compact] amount: BalanceOf<T, I>,
+			beneficiary: <T::Lookup as StaticLookup>::Source,
+		) -> DispatchResult {
+			let max_amount = T::SpendOrigin::ensure_origin(origin)?;
+			let beneficiary = T::Lookup::lookup(beneficiary)?;
+
+			ensure!(amount <= max_amount, Error::<T, I>::InsufficientPermission);
+			let proposal_index = Self::proposal_count();
+			Approvals::<T, I>::try_append(proposal_index)
+				.map_err(|_| Error::<T, I>::TooManyApprovals)?;
+			let proposal = Proposal {
+				proposer: beneficiary.clone(),
+				value: amount,
+				beneficiary: beneficiary.clone(),
+				bond: Default::default(),
+			};
+			Proposals::<T, I>::insert(proposal_index, proposal);
+			ProposalCount::<T, I>::put(proposal_index + 1);
+
+			Self::deposit_event(Event::SpendApproved { proposal_index, amount, beneficiary });
+			Ok(())
+		}
+
 		/// Force a previously approved proposal to be removed from the approval queue.
 		/// The original deposit will no longer be returned.
 		///