readme updates (#1230)

will merge after api release

Author: davidzhao

livekit-api/README.md

@@ -2,4 +2,140 @@
 
 The official server API crate for [LiveKit](https://livekit.com).
 
-Use this crate to generate access tokens and invoke LiveKit server APIs for agent dispatch, ingress, egress, SIP, and more.
+Use this crate to generate access tokens and invoke LiveKit server APIs for rooms, egress, ingress, SIP, agent dispatch, and more.
+
+## Server API
+
+`LiveKitApi` is a single entry point to every server API, exposing each service through an accessor (`room()`, `egress()`, `ingress()`, `sip()`, `agent_dispatch()`, `connector()`).
+
+```rust,no_run
+use livekit_api::services::LiveKitApi;
+use livekit_api::services::room::CreateRoomOptions;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let lk = LiveKitApi::with_api_key("https://my.livekit.host", "my-key", "my-secret");
+
+    let room = lk
+        .room()
+        .create_room(
+            "my-room",
+            CreateRoomOptions { empty_timeout: 600, max_participants: 20, ..Default::default() },
+        )
+        .await?;
+
+    println!("created room {}", room.name);
+    Ok(())
+}
+```
+
+Individual service clients (`RoomClient`, `SIPClient`, etc.) can also be created directly with the same constructors.
+
+### Authentication
+
+The server API supports two modes of operation:
+
+- **API key & secret** — recommended for backend use. `LiveKitApi::new(host)` reads the key and secret from the `LIVEKIT_API_KEY` and `LIVEKIT_API_SECRET` environment variables; `LiveKitApi::with_api_key(host, key, secret)` takes them explicitly instead. Either way, a short-lived token is signed for each request.
+- **Access token** — for client-side use where the API secret must not be exposed. `LiveKitApi::with_token(host, token)` sends a pre-signed [access token](https://docs.livekit.io/frontends/reference/tokens-grants/) verbatim on every request; its grants must cover the calls you make.
+
+### Agent dispatch
+
+Explicitly dispatch an agent into a room (see [Agent dispatch](https://docs.livekit.io/agents/server/agent-dispatch/)):
+
+```rust,no_run
+use livekit_api::services::LiveKitApi;
+use livekit_protocol as proto;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let lk = LiveKitApi::with_api_key("https://my.livekit.host", "my-key", "my-secret");
+
+    lk.agent_dispatch()
+        .create_dispatch(proto::CreateAgentDispatchRequest {
+            room: "my-room".to_owned(),
+            agent_name: "my-agent".to_owned(),
+            ..Default::default()
+        })
+        .await?;
+    Ok(())
+}
+```
+
+### Error handling
+
+Service methods return `ServiceResult<T>` (`Result<T, ServiceError>`). A failed server call is a `ServiceError::Twirp(ServerError)`; when the server returns a structured error it is `ServerError::Twirp(ServerErrorCode)`, which carries the error code and message. (`ServerError`'s former `TwirpError`/`TwirpErrorCode`/`TwirpResult` type names remain as deprecated aliases.)
+
+```rust,no_run
+use livekit_api::services::LiveKitApi;
+
+#[tokio::main]
+async fn main() {
+    let lk = LiveKitApi::with_api_key("https://my.livekit.host", "my-key", "my-secret");
+    match lk.room().delete_room("my-room").await {
+        Ok(_) => {}
+        Err(e) => eprintln!("delete_room failed: {e}"),
+    }
+}
+```
+
+### Handling SIP call errors
+
+When a SIP call fails (e.g. the callee is busy or declines), the server attaches a SIP status to the error. `SipCallError::from_error` decodes it from a returned error, exposing the SIP status code and reason:
+
+```rust,no_run
+use livekit_api::services::sip::CreateSIPParticipantOptions;
+use livekit_api::services::{LiveKitApi, SipCallError};
+
+#[tokio::main]
+async fn main() {
+    let lk = LiveKitApi::with_api_key("https://my.livekit.host", "my-key", "my-secret");
+
+    let result = lk
+        .sip()
+        .create_sip_participant(
+            "ST_trunk".to_owned(),
+            "+15105550100".to_owned(),
+            "my-room".to_owned(),
+            CreateSIPParticipantOptions {
+                wait_until_answered: Some(true),
+                ..Default::default()
+            },
+            None,
+        )
+        .await;
+
+    if let Err(err) = result {
+        if let Some(sip) = SipCallError::from_error(&err) {
+            eprintln!("{sip}"); // e.g. "SIP call failed: 486 Busy Here (resource_exhausted)"
+            if sip.sip_status_code() == Some(486) {
+                // callee is busy
+            }
+        }
+    }
+}
+```
+
+## Access tokens
+
+Access tokens are generated with `AccessToken`:
+
+```rust,no_run
+use livekit_api::access_token::{AccessToken, VideoGrants};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let token = AccessToken::with_api_key("my-key", "my-secret")
+        .with_identity("participant-identity")
+        .with_name("Participant Name")
+        .with_grants(VideoGrants {
+            room_join: true,
+            room: "my-room".to_owned(),
+            ..Default::default()
+        })
+        .to_jwt()?;
+
+    println!("{token}");
+    Ok(())
+}
+```
+
+By default, tokens expire 6 hours after generation. Override this with `.with_ttl(duration)`.