Add ABI crate

Call and Event are both from the pallets, which are AGPL licensed. Accordingly,
they make serai-client AGPL licensed when serai-client must end up MIT
licensed. This creates a MIT-licensed variant of Calls and Events such that
they can be used by serai-client, enabling transitioning it to MIT.

Relevant to https://github.com/serai-dex/serai/issues/337.

substrate/abi/src/dex.rs

@@ -0,0 +1,77 @@
+use sp_runtime::BoundedVec;
+
+use serai_primitives::*;
+
+type PoolId = Coin;
+type PoolCoinId = Coin;
+type MaxSwapPathLength = sp_core::ConstU32<3>;
+
+#[derive(Clone, PartialEq, Eq, Debug, scale::Encode, scale::Decode)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub enum Call {
+  add_liquidity {
+    coin: Coin,
+    coin_desired: SubstrateAmount,
+    sri_desired: SubstrateAmount,
+    coin_min: SubstrateAmount,
+    sri_min: SubstrateAmount,
+    mint_to: SeraiAddress,
+  },
+  remove_liquidity {
+    coin: Coin,
+    lp_token_burn: SubstrateAmount,
+    coin_min_receive: SubstrateAmount,
+    sri_min_receive: SubstrateAmount,
+    withdraw_to: SeraiAddress,
+  },
+  swap_exact_tokens_for_tokens {
+    path: BoundedVec<Coin, MaxSwapPathLength>,
+    amount_in: SubstrateAmount,
+    amount_out_min: SubstrateAmount,
+    send_to: SeraiAddress,
+  },
+  swap_tokens_for_exact_tokens {
+    path: BoundedVec<Coin, MaxSwapPathLength>,
+    amount_out: SubstrateAmount,
+    amount_in_max: SubstrateAmount,
+    send_to: SeraiAddress,
+  },
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, scale::Encode, scale::Decode)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub enum Event {
+  PoolCreated {
+    pool_id: PoolId,
+    pool_account: SeraiAddress,
+    lp_token: PoolCoinId,
+  },
+
+  LiquidityAdded {
+    who: SeraiAddress,
+    mint_to: SeraiAddress,
+    pool_id: PoolId,
+    coin_amount: SubstrateAmount,
+    sri_amount: SubstrateAmount,
+    lp_token: PoolCoinId,
+    lp_token_minted: SubstrateAmount,
+  },
+
+  LiquidityRemoved {
+    who: SeraiAddress,
+    withdraw_to: SeraiAddress,
+    pool_id: PoolId,
+    coin_amount: SubstrateAmount,
+    sri_amount: SubstrateAmount,
+    lp_token: PoolCoinId,
+    lp_token_burned: SubstrateAmount,
+  },
+
+  SwapExecuted {
+    who: SeraiAddress,
+    send_to: SeraiAddress,
+    path: BoundedVec<Coin, MaxSwapPathLength>,
+    amount_in: SubstrateAmount,
+    amount_out: SubstrateAmount,
+  },
+}