A Social Account Recovery Pallet (#4531)

* Initial sketch of social recovery pallet

* Fix compilation issues

* Use a single total delay, rename stuff

* Check possible overflow

* Copyright bump

* Add mock for tests

* Add basic end to end test

* Add `create_recovery` tests

* Add malicious recovery lifecycle test

* Make clear we check for sorted and unique friends

* Work on some tests, clean up imports

* Change `if let Some(_)` to `ok_or()`

* More tests

* Finish tests, except issue with `on_free_balance_zero`

* Fix `on_free_balance_zero`

* Pallet docs

* Add function/weight docs

* Fix merge master

* OnReapAccount for System too

* Update weight docs

* Allow passthrough to support fee-less extrinsics

Cargo.toml

@@ -78,6 +78,7 @@ members = [
 	"frame/nicks",
 	"frame/offences",
 	"frame/randomness-collective-flip",
+	"frame/recovery",
 	"frame/scored-pool",
 	"frame/session",
 	"frame/society",

frame/recovery/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "pallet-recovery"
+version = "2.0.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+serde = { version = "1.0.101", optional = true }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
+enumflags2 = { version = "0.6.2" }
+sp-std = { version = "2.0.0", default-features = false, path = "../../primitives/std" }
+sp-io = { version = "2.0.0", default-features = false, path = "../../primitives/io" }
+sp-runtime = { version = "2.0.0", default-features = false, path = "../../primitives/runtime" }
+frame-support = { version = "2.0.0", default-features = false, path = "../support" }
+frame-system = { version = "2.0.0", default-features = false, path = "../system" }
+
+[dev-dependencies]
+sp-core = { version = "2.0.0", path = "../../primitives/core" }
+pallet-balances = { version = "2.0.0", path = "../balances" }
+
+[features]
+default = ["std"]
+std = [
+	"serde",
+	"codec/std",
+	"sp-std/std",
+	"sp-io/std",
+	"sp-runtime/std",
+	"frame-support/std",
+	"frame-system/std",
+]