rpc server: listen to ipv6 socket if available and --experimental-rpc-endpoint CLI option

prdoc/pr_4792.prdoc

@@ -1,7 +1,7 @@
 # Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
 # See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
 
-title: "rpc: bind to `ipv6` if available and add `CLI --rpc-endpoint` to specify listen addr"
+title: "rpc: bind to `ipv6` if available and add `CLI --experimental-rpc-endpoint` to specify listen addr"
 
 doc:
   - audience: Node Operator
@@ -10,16 +10,17 @@ doc:
 
       1. The default setting is that substrate starts a rpc server that listens to localhost both ipv4 and ipv6 on the same port. 
          ipv6 is allowed to fail because some platforms may not support it
-      2. A new RPC CLI option `--rpc-endpoint` is introduced which allows to configure arbitrary listen addresses including the port, 
+      2. A new RPC CLI option `--experimental-rpc-endpoint` is introduced which allows to configure arbitrary listen addresses including the port, 
          if this is enabled no other interfaces are enabled.
       3. If the local addr is not found for any of the sockets the server is not started and throws an error.
       4. Remove the deny_unsafe from the RPC implementations instead this is an extension to allow different polices for different interfaces/sockets 
          such one may enable unsafe on local interface and safe on only the external interface.
-      5. This new `--rpc-endpoint` has several options and in the help menu all possible parameters are documented.
+      5. This new `--experimental-rpc-endpoint` has several options and in the help menu all possible parameters are documented.
+      6. The log emitted by jsonrpc server when it has been started has been modified to indicate all started rpc endpoints. 
 
       So for instance it's now possible to start up three RPC endpoints as follows:
       ```
-      $ polkadot --rpc-endpoint "listen-addr=127.0.0.1:9944,methods=unsafe" --rpc-endpoint "listen-addr=0.0.0.0:9945,methods=safe,rate-limit=100" --rpc-endpoint "listen-addr=[::1]:9944,optional=true"
+      $ polkadot --experimental-rpc-endpoint "listen-addr=127.0.0.1:9944,methods=unsafe" --experimental-rpc-endpoint "listen-addr=0.0.0.0:9945,methods=safe,rate-limit=100" --experimental-rpc-endpoint "listen-addr=[::1]:9944,optional=true"
       ```
 
 crates:

substrate/client/cli/src/commands/run_cmd.rs

@@ -128,11 +128,12 @@ pub struct RunCmd {
 	#[arg(long, value_name = "PORT")]
 	pub rpc_port: Option<u16>,
 
-	/// Specify the JSON-RPC server interface and this option which can be enabled several times if
-	/// you want expose several RPC interfaces with different configurations.
+	/// EXPERIMENTAL: Specify the JSON-RPC server interface and this option which can be enabled
+	/// several times if you want expose several RPC interfaces with different configurations.
 	///
-	/// The format for this option is: `--rpc-endpoint"listen-addr=<ip:port>,<key=value>,..."`
-	/// where each option is separated by a comma and `listen-addr` is the only required param.
+	/// The format for this option is:
+	/// `--experimental-rpc-endpoint"listen-addr=<ip:port>,<key=value>,..."` where each option is
+	/// separated by a comma and `listen-addr` is the only required param.
 	///
 	/// The following options are available:
 	///  • listen-addr: The socket address (ip:port) to listen on. Be careful to not expose the
@@ -157,13 +158,15 @@ pub struct RunCmd {
 	///  • rate-limit-trust-proxy-headers: Trust proxy headers for disable rate limiting (optional)
 	///  • rate-limit-whitelisted-ips: Disable rate limiting for certain ip addresses (optional)
 	///  • retry-random-port: If the port is already in use, retry with a random port (optional)
+	///
+	/// Use with care, this flag is unstable and subject to change.
 	#[arg(
 		long,
 		num_args = 1..,
 		verbatim_doc_comment,
 		conflicts_with_all = &["rpc_external", "unsafe_rpc_external", "rpc_port", "rpc_cors", "rpc_rate_limit_trust_proxy_headers", "rpc_rate_limit", "rpc_rate_limit_whitelisted_ips", "rpc_message_buffer_capacity_per_connection", "rpc_disable_batch_requests", "rpc_max_subscriptions_per_connection", "rpc_max_request_size", "rpc_max_response_size"]
 	)]
-	pub rpc_endpoint: Vec<RpcEndpoint>,
+	pub experimental_rpc_endpoint: Vec<RpcEndpoint>,
 
 	/// Maximum number of RPC server connections.
 	#[arg(long, value_name = "COUNT", default_value_t = RPC_DEFAULT_MAX_CONNECTIONS)]
@@ -448,8 +451,8 @@ impl CliConfiguration for RunCmd {
 	}
 
 	fn rpc_addr(&self, default_listen_port: u16) -> Result<Option<Vec<RpcEndpoint>>> {
-		if !self.rpc_endpoint.is_empty() {
-			for endpoint in &self.rpc_endpoint {
+		if !self.experimental_rpc_endpoint.is_empty() {
+			for endpoint in &self.experimental_rpc_endpoint {
 				// Technically, `0.0.0.0` isn't a public IP address, but it's a way to listen on
 				// all interfaces. Thus, we consider it as a public endpoint and warn about it.
 				if endpoint.rpc_methods == RpcMethods::Unsafe && endpoint.is_global() ||
@@ -462,7 +465,7 @@ impl CliConfiguration for RunCmd {
 				}
 			}
 
-			return Ok(Some(self.rpc_endpoint.clone()));
+			return Ok(Some(self.experimental_rpc_endpoint.clone()));
 		}
 
 		let (ipv4, ipv6) = rpc_interface(