(untested) sanitize code

* remove peer argument from scrape swarm storage call

* replace Peer field with netip.Addr in ScrapeRequest

* add man for keydb storage

* update readme

docs/storage/keydb.md

@@ -0,0 +1,46 @@
+# KeyDB Storage
+
+This storage mainly the same as Redis and uses some of [redis](redis.md) store logic
+with next exceptions:
+
+* peers stored in [sets](https://redis.io/docs/manual/data-types/#sets) 
+instead of [hashes](https://redis.io/docs/manual/data-types/#hashes);
+
+* keys such as `CHI_I`, `CHI_S_C` and `CHI_L_C` not used (at all);
+
+* peer TTL relies on KeyDB's [EXPIREMEMBER](https://docs.keydb.dev/docs/commands/#expiremember) 
+command, so MoChi does not need to periodically check peer expiration;
+
+* storage does not execute periodical statistics collection (peer/lecher/info hash count)
+because:
+  * manual calculation (INC/DEC peers count) is not usable 
+  * manual scan of all keys is quite expensive operation.
+
+## Use Case
+
+KeyDB is fork of Redis, which allows to create active-active cluster and set `set` member expiration,
+so this type of backend can be used to create fully symmetric cluster of tracker nodes with minimum
+overkill to garbage collection.
+
+## Configuration
+
+Configuration options are the same as [redis's](redis.md#Configuration), **BUT**:
+
+* `name` should be set to `keydb` instead of `redis`;
+
+* `gc_interval` and `prometheus_reporting_interval` don't have any sense.
+
+```yaml
+mochi:
+  storage:
+    name: keydb
+    config:
+	...
+```
+
+## Implementation
+
+KeyDB storage uses same key names as `redis` (`CHI_S4_<HASH>`, `CHI_L6_<HASH>`...) to store peers,
+but it is **impossible** to switch between storage providers without deleting these keys.
+You **can** use `redis` storage type with KeyDB instance (KeyDB supports all Redis commands),
+but **not** `keydb` storage type with Redis instance.