Update CHANGELOG

CHANGELOG.md

@@ -14,6 +14,39 @@ The following emojis are used to highlight certain changes:
 
 ## [Unreleased]
 
+- `bitswap`, `routing`, `exchange` ([#641](https://github.com/ipfs/boxo/pull/641)):
+  * ✨ Bitswap is no longer in charge of providing blocks to the newtork: providing functionality is now handled by a `exchange/providing.Exchange`, meant to be used with `provider.System` so that all provides follow the same rules (multiple parts of the code where handling provides) before.
+  * 🛠 `bitswap/client/internal/providerquerymanager` has been moved to `routing/providerquerymanager` where it belongs. In order to keep compatibility, Bitswap now receives a `routing.ContentDiscovery` parameter which implements `FindProvidersAsync(...)` and uses it to create a `providerquerymanager` with the default settings as before. Custom settings can be used by using a custom `providerquerymanager` to manually wrap a `ContentDiscovery` object and pass that in as `ContentDiscovery` on initialization while setting `bitswap.WithDefaultProviderQueryManager(false)` (to avoid re-wrapping it again).
+  * The renovated `providedQueryManager` will trigger lookups until it manages to connect to `MaxProviders`. Before it would lookup at most `MaxInProcessRequests*MaxProviders` and connection failures may have limited the actual number of providers found.
+  * 🛠 We have aligned our routing-related interfaces with the libp2p [`routing`](https://pkg.go.dev/github.com/libp2p/go-libp2p/core/routing#ContentRouting) ones, including in the `reprovider.System`.
+  * In order to obtain exactly the same behaviour as before (i.e. particularly ensuring that new blocks are still provided), what was done like:
+
+```go
+	bswapnet := network.NewFromIpfsHost(host, contentRouter)
+	bswap := bitswap.New(p.ctx, bswapnet, blockstore)
+	bserv = blockservice.New(blockstore, bswap)
+```
+	needs to be done like:
+
+```go
+	// Create network: no contentRouter anymore
+	bswapnet := network.NewFromIpfsHost(host)
+	// Create Bitswap: a new "discovery" parameter, usually the "contentRouter"
+	// which does both discovery and providing.
+	bswap := bitswap.New(p.ctx, bswapnet, discovery, blockstore)
+	// A provider system that handles concurrent provides etc. "contentProvider"
+	// is usually the "contentRouter" which does both discovery and providing.
+	// "contentProvider" could be used directly without wrapping, but it is recommended
+	// to do so to provide more efficiently.
+	provider := provider.New(datastore, provider.Online(contentProvider)
+	// A wrapped providing exchange using the previous exchange and the provider.
+	exch := providing.New(bswap, provider)
+
+	// Use exch instead from now on.
+	...
+```
+
+
 ### Added
 
 - `routing/http/server`: added built-in Prometheus instrumentation to http delegated `/routing/v1/` endpoints, with custom buckets for response size and duration to match real world data observed at [the `delegated-ipfs.dev` instance](https://docs.ipfs.tech/concepts/public-utilities/#delegated-routing). [#718](https://github.com/ipfs/boxo/pull/718) [#724](https://github.com/ipfs/boxo/pull/724)