finalize opportunity adapter docs dump

Author: anihamde

pages/express-relay/how-express-relay-works/opportunities.mdx

@@ -27,6 +27,8 @@ The Opportunity Adapter contract enables searchers to engage with opportunities
 
 Thus, the Opportunity Adapter unifies the disparate interfaces of different protocols with respect to their different opportunities. This unification in a single interface is what makes Express Relay an opportunity hub connecting protocols and searchers.
 
+To use the Opportunity Adapter workflow, a searcher submits a bid with the target contract set to the `OpportunityAdapterFactory` contract. Each searcher has their own `OpportunityAdapter` contract per chain that is created when they first interact with `OpportunityAdapterFactory`. The factory contract then routes the transaction of a searcher to its corresponding `OpportunityAdapter` contract.
+
 ### Permit2
 
 The `OpportunityAdapter` contract uses the [Permit2](https://github.com/Uniswap/permit2) token approval system, which handles the validation of a searcher's signature. Permit2 enables users to authorize token approvals for specific transaction data. In combination with Permit2, `OpportunityAdapter` allows a searcher to authorize use of their tokens only with a call to a particular contract with specified calldata and conditional on receipt of a set of specified `buyTokens`.

pages/express-relay/integrate-as-searcher.mdx

@@ -8,3 +8,5 @@ The integration consists of 2 main steps:
 
 - Integrate your searcher service with the [auction server](./integrate-as-searcher/auction-server)
 - \[Optional\] Use [OpportunityAdapter](./integrate-as-searcher/opportunity-adapter) and setup a wallet with the necessary tokens and approvals
+
+You can also find a list of relevant contract addresses [here](./contract-addresses).

pages/express-relay/integrate-as-searcher/auction-server.mdx

@@ -146,20 +146,26 @@ If you prefer to use your own custom contracts rather than the `OpportunityAdpat
 ```solidity
 ...
 function callLiquidation(Opportunity memory opp){
+    for (uint i=0; i<opp.sell_tokens.length; i++) {
+        let token = opp.sell_tokens[i];
+        IERC20(token.contract).approve(opp.contract, token.amount);
+    }
 
-    // this is a simplified version since sell and buy tokens are
-    // an array and multiple assets may be necessary for the liquidation
-    assert(opp.buy_tokens.length == 1);
-    assert(opp.sell_tokens.length == 1);
-
-    IERC20(opp.sell_tokens[0].contract).approve(opp.contract, opp.sell_tokens[0].amount);
-
-    before = IERC20(opp.buy_tokens[0].contract).balanceOf(address(this));
+    uint256[] before = new uint256[](opp.buy_tokens.length);
+    for (uint j=0; j<opp.buy_tokens.length; j++) {
+        let token = opp.buy_tokens[j];
+        before = IERC20(token.contract).balanceOf(address(this));
+    }
+        
     opp.target_contract.call{value: opp.target_call_value}(opp.target_calldata);
 
-    after = IERC20(opp.buy_tokens[0].target_contract).balanceOf(address(this));
+    uint256[] after = new uint256[](opp.buy_tokens.length);
+    for (uint j=0; j<opp.buy_tokens.length; j++) {
+        let token = opp.buy_tokens[j];
+        after = IERC20(token.target_contract).balanceOf(address(this));
 
-    assert(after == before + opportunity.buy_tokens[0].amount)
+        assert(after[j] == before[j] + token.amount);
+    }
 }
 ...
 ```

pages/express-relay/integrate-as-searcher/opportunity-adapter.mdx

@@ -1 +1,8 @@
 # Integrate with opportunity adapter
+
+The `OpportunityAdapter` is a utility contract that can be used for easier integration with express relay while maintaining maximum security. In this integration, searchers use the `Permit2` contract for safe asset management (`ERC20` tokens and Wrapped ETH) and the adapter contract to transfer bids, execute the opportunity, and ensure the assets are transferred correctly. Using the `OpportunityAdapter` means that a searcher does not need to deploy their own custom contract for inventory management and routing to the protocol contracts where liquidation takes place.
+
+After [integrating with the auction server](./auction-server), you can integrate with the `OpportunityAdapter` framework via the following steps:
+1. Hold your assets in your wallet. You will need to own all assets you expect to provide as `sell_tokens` to different opportunities. You will also need to approve `WETH`, as the `OpportunityAdapter` will pay your bids by deducting the bid amounts from your wallet's `WETH` balance.
+2. Approve your assets to the `Permit2` contract, `0x000000000022D473030F116dDEE9F6B43aC78BA3`.
+3. When bidding, set `target_contract` to the `OpportunityAdapterFactory` and craft your `target_calldata` based on the format of the `OpportunityAdapter`. The express relay [JavaScript SDK](https://www.npmjs.com/package/@pythnetwork/express-relay-evm-js) and [Python SDK](https://pypi.org/project/express-relay/) have helper functions that handle this step for you.