routing/http: simplify GetClosestPeers endpoint

changed path parameter from {peer-id} to {key} to accept both CIDs and
Peer IDs, matching actual DHT usage where closest peers can be queried
for arbitrary keys

removed count and closer-than query parameters that were adding
complexity without clear use cases in practice

clarified response size should match DHT bucket size (20 for Amino DHT)

added note that this optional endpoint helps light clients lower the
cost of DHT walks in browser contexts

Author: lidel

src/routing/http-routing-v1.md

@@ -246,19 +246,16 @@ The content body must be a [`application/vnd.ipfs.ipns-record`][application/vnd.
 
 ## DHT Routing API
 
-### `GET /routing/v1/dht/closest/peers/{peer-id}`
+### `GET /routing/v1/dht/closest/peers/{key}`
 
-#### Path Parameters
-
-- `peer-id` is a [Peer ID](https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md) represented as a CIDv1 encoded with `libp2p-key` codec.
+This optional endpoint allows light clients to lower the cost of DHT walks in browser contexts.
 
-#### Query Parameters
+#### Path Parameters
 
-- `closer-than` is an optional [Peer ID](https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md) represented as a CIDv1 encoded with `libp2p-key` codec.
-  - Returned peer records must be closer to `peer-id` than `closer-than`.
-  - If omitted the routing implementation should use its own [Peer ID](https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md).
-- `count` is an optional number that specifies how many peer records the requester desires.
-  - Minimum 1, maximum 100, default 20.
+- `key` is a [CID] or [Peer ID][peer-id-representation] to find the closest peers to.
+  - [CID] should be a CIDv1 in any encoding.
+  - [Peer ID][peer-id-representation] can be represented as a Multihash in Base58btc, or a CIDv1 with `libp2p-key` (`0x72`) codec in Base36 or Base32.
+  - Implementations SHOULD support both CID and Peer ID formats for maximum interoperability.
 
 #### Response Status Codes
 
@@ -294,7 +291,7 @@ The content body must be a [`application/vnd.ipfs.ipns-record`][application/vnd.
 }
 ```
 
-The number of peer records in the responses SHOULD be limited to the `count` query parameter, which defaults to 20 if unspecified.
+The number of peer records in the response SHOULD be limited to the DHT bucket size (20 for Amino DHT).
 
 The client SHOULD be able to make a request with `Accept: application/x-ndjson` and get a [stream](#streaming) with more results.