docs: deprecate relay v1

this adds clear messaging that V1 is no more,
refusing to run for users who are still using this project
to provide RelayV1. The goal here is to inform them they use deprecated
protocol that is no longer supported by the swarm.

README.md

@@ -1,3 +1,11 @@
+> [!WARNING]
+> # No longer maintained. No longer relevant.
+>
+> This project is no longer maintained, was used in transitional period when ecosystem was switching from V1 to [V2](https://github.com/libp2p/specs/blob/master/relay/circuit-v2.md).
+> `go-libp2p` >= `v0.26.0` [no longer supports Relay V1](https://github.com/libp2p/go-libp2p/issues/2075), making this project outdated.
+>
+> Modern deployments should implement their own relay setups based on [Relay V2 protocol](https://github.com/libp2p/specs/blob/master/relay/circuit-v2.md), which is supported via [go-libp2p](https://github.com/libp2p/go-libp2p) and `libp2p.EnableRelayService`
+
 # libp2p-relay-daemon
 
 > A standalone daemon that provides libp2p circuit relay services,

cmd/libp2p-relay-daemon/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"net/http"
@@ -108,16 +109,16 @@ func main() {
 		panic(err)
 	}
 
-	if cfg.RelayV2.Enabled {
-		fmt.Printf("Starting RelayV2...\n")
-		_, err = relayv2.New(host,
-			relayv2.WithResources(cfg.RelayV2.Resources),
-			relayv2.WithACL(acl))
-		if err != nil {
-			panic(err)
-		}
-		fmt.Printf("RelayV2 is running!\n")
+	if !cfg.RelayV2.Enabled {
+		panic(errors.New("RelayV2.Enabled=false is no longer supported. V2 is the only supported version now (https://github.com/libp2p/go-libp2p/issues/2075)"))
+	}
+	_, err = relayv2.New(host,
+		relayv2.WithResources(cfg.RelayV2.Resources),
+		relayv2.WithACL(acl))
+	if err != nil {
+		panic(err)
 	}
+	fmt.Printf("RelayV2 is running!\n")
 
 	select {}
 }

version.json

@@ -1,3 +1,3 @@
 {
-  "version": "v0.4.0"
+  "version": "v0.5.0"
 }