RouterV2 (#117)

The `RouterV2` contract supports swaps along paths that include `Pair`
and `StablePool` types of pools.

### Swap Path
Each `swap*` method takes as the arguments `path: Vec<Step>` and
`token_out: AccountId`, except for the `swap*_for_native` - here we know
that the `token_out` is always the `wrapped_native` token.

The `Step` struct has two fields: `Step { token_in: AccountId, pool_id:
AccountId }`. A valid path must consist of at least one `Step`.

E.g `path: [Step(token_a, pool_1) , Step(token_b, pool_2) ], token_out:
token_c` can be visualized like this:
```shell
        pool_1          pool_2
       /      \        /      \ 
token_a   ->   token_b    ->    token_c
```

### Compatibility
The old Router had a "pair caching" mechanism which allowed caching
custom `Pair` contracts. Also, when adding liquidity to a non-existent
pair, the pair was created via the `Factory` contract.

In the new Router, when adding liquidity to a `Pair` pool, the caller
has an option to provide the `Pair` address. If the address is not
provided, the contract calls the `Factory` to create a new Pair. It
fails if `Pair` for given tokens already exists.

The new Router caches pools solely for optimization purposes. It is
allowed to swap through any valid pool contract (`Pair` or
`StablePool`). The pools are cached when swapping through or managing
liquidity in a valid pool (permissionless).

Author: JanKuczma

Cargo.lock

@@ -7,7 +7,7 @@ help: # Show help for each of the Makefile recipes.
 AMM_CONTRACTS = ./contracts
 AMM_CONTRACTS_PATHS := $(shell find $(AMM_CONTRACTS) -mindepth 1 -maxdepth 1 -type d)
 
-CONTRACTS := factory_contract pair_contract router_contract stable_pool_contract mock_rate_provider_contract
+CONTRACTS := factory_contract pair_contract router_contract router_v2_contract stable_pool_contract mock_rate_provider_contract
 
 INK_DEV_IMAGE := "public.ecr.aws/p6e8q1z1/ink-dev:2.1.0"
 SCRIPT_DIR := $(shell cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )

amm/Makefile

@@ -0,0 +1,39 @@
+[package]
+name = "router_v2_contract"
+version = "0.1.0"
+authors = ["Cardinal Cryptography"]
+edition = "2021"
+
+[dependencies]
+ink = { version = "=4.3.0", default-features = false }
+
+scale = { package = "parity-scale-codec", version = "3", default-features = false, features = [
+    "derive",
+] }
+scale-info = { version = "2.9", default-features = false, features = [
+    "derive",
+], optional = true }
+
+psp22 = { version = "=0.2.2", default-features = false }
+wrapped-azero = { git = "https://github.com/Cardinal-Cryptography/wAZERO.git", default-features = false, features = [
+    "ink-as-dependency",
+] }
+
+traits = { path = "../../traits", default-features = false }
+amm-helpers = { path = "../../../helpers", default-features = false }
+
+[lib]
+name = "router_v2_contract"
+path = "lib.rs"
+
+[features]
+default = ["std"]
+std = [
+    "ink/std",
+    "psp22/std",
+    "scale/std",
+    "scale-info",
+    "scale-info/std",
+    "traits/std",
+]
+ink-as-dependency = []