docs: add client methods (service invocation/state management/pubsub)

Signed-off-by: mikeee <[email protected]>

Author: mikeee

daprdocs/content/en/rust-sdk-docs/rust-client/_index.md

@@ -7,7 +7,9 @@ description: How to get up and running with the Dapr Rust SDK
 no_list: true
 ---
 
-The Dapr client package allows you to interact with other Dapr applications from a Go application.
+The Dapr client package allows you to interact with other Dapr applications from a Rust application.
+
+> **Note:** The Rust SDK is currently in Alpha/WIP state and is constantly evolving.
 
 ## Prerequisites
 
@@ -31,5 +33,66 @@ You can either reference `dapr::Client` or bind the full path to a new name as f
 use dapr::Client as DaprClient
 ```
 
+
+## Building blocks
+
+The Rust SDK allows you to interface with the [Dapr building blocks]({{< ref building-blocks >}}).
+
+### Service Invocation
+
+To invoke a specific method on another service running with Dapr sidecar, the Dapr client Go SDK provides two options:
+
+Invoke a service
+```rust
+let response = client
+    .invoke_service("service-to-invoke", "method-to-invoke", Some(data))
+    .await
+    .unwrap();
+```
+
+
+For a full guide on service invocation, visit [How-To: Invoke a service]({{< ref howto-invoke-discover-services.md >}}).
+
+### State Management
+
+The Dapr Client provides access to these state management methods:  `save_state`, `get_state`, `delete_state` that can be used like so:
+
+```rust
+let store_name = "store-name";
+let state_key = "state-key";
+
+let states = vec![(state_key, ("state-value").as_bytes().to_vec())];
+
+// save state with the key "state-key" and value "state-value"
+client.save_state(store_name, states).await?;
+
+// get state for key "state-key"
+let response = client.get_state(store_name, state_key, None).await.unwrap();
+
+// delete state for key "state-key"
+client.delete_state(store_name, state_key, None).await?;
+```
+
+> **Note:** The `save_state` method currently performs a 'bulk' save but this will be refactored
+
+
+For a full guide on state management, visit [How-To: Save & get state]({{< ref howto-get-save-state.md >}}).
+
+### Publish Messages
+To publish data onto a topic, the Dapr Go client provides a simple method:
+
+```rust
+let pubsub_name = "pubsub-name".to_string();
+let pubsub_topic = "topic-name".to_string();
+let pubsub_content_type = "text/plain".to_string();
+
+let data = "content".to_string().into_bytes();
+client
+    .publish_event(pubsub_name, pubsub_topic, pubsub_content_type, data, None)
+    .await?;
+```
+
+For a full guide on pub/sub, visit [How-To: Publish & subscribe]({{< ref howto-publish-subscribe.md >}}).
+
 ## Related links
 [Rust SDK Examples](https://github.com/dapr/rust-sdk/tree/master/examples)