Repot frame_support::traits; introduce some new currency stuff (#8435)

* Reservable, Transferrable Fungible(s), plus adapters.

* Repot into new dir

* Imbalances for Fungibles

* Repot and balanced fungible.

* Clean up names and bridge-over Imbalanced.

* Repot frame_support::trait. Finally.

* Make build.

* Docs

* Good errors

* Fix tests. Implement fungible::Inspect for Balances.

* Implement additional traits for Balances.

* Revert UI test "fixes"

* Fix UI error

* Fix UI test

* Fixes

* Update lock

* Grumbles

* Grumbles

* Fixes

Co-authored-by: Bastian Köcher <info@kchr.de>

substrate/frame/support/src/traits/storage.rs

@@ -0,0 +1,45 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2019-2021 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Traits for encoding data related to pallet's storage items.
+
+/// An instance of a pallet in the storage.
+///
+/// It is required that these instances are unique, to support multiple instances per pallet in the same runtime!
+///
+/// E.g. for module MyModule default instance will have prefix "MyModule" and other instances
+/// "InstanceNMyModule".
+pub trait Instance: 'static {
+	/// Unique module prefix. E.g. "InstanceNMyModule" or "MyModule"
+	const PREFIX: &'static str;
+}
+
+/// An instance of a storage in a pallet.
+///
+/// Define an instance for an individual storage inside a pallet.
+/// The pallet prefix is used to isolate the storage between pallets, and the storage prefix is
+/// used to isolate storages inside a pallet.
+///
+/// NOTE: These information can be used to define storages in pallet such as a `StorageMap` which
+/// can use keys after `twox_128(pallet_prefix())++twox_128(STORAGE_PREFIX)`
+pub trait StorageInstance {
+	/// Prefix of a pallet to isolate it from other pallets.
+	fn pallet_prefix() -> &'static str;
+
+	/// Prefix given to a storage to isolate from other storages in the pallet.
+	const STORAGE_PREFIX: &'static str;
+}