add secretsmanager helloworld example (#303) (#304)

* add secrets manager hello world example

* Apply suggestions from code review

Co-authored-by: Russell Cohen <russell.r.cohen@gmail.com>

Co-authored-by: Russell Cohen <russell.r.cohen@gmail.com>

Co-authored-by: Russell Cohen <russell.r.cohen@gmail.com>

aws/sdk/examples/secretsmanager-helloworld/Cargo.toml

+[package]
+name = "secretsmanager-helloworld"
+version = "0.1.0"
+authors = ["AWS Rust SDK Team <aws-sdk-rust@amazon.com>", "Nas Taibi <naceredd@amazon.com>"]
+edition = "2018"
+description = "Example usage of the SecretManager service"
+
+[dependencies]
+secretsmanager = { path = "../../build/aws-sdk/secretsmanager" }
+aws-hyper = { path = "../../build/aws-sdk/aws-hyper" }
+tokio = { version = "1", features = ["full"]}
+# optional
+tracing-subscriber = { version = "0.2.16", features = ["fmt"] }

aws/sdk/examples/secretsmanager-helloworld/src/main.rs

+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+use aws_hyper::conn::Standard;
+use secretsmanager::Client;
+use secretsmanager::Region;
+use tracing_subscriber::fmt::format::FmtSpan;
+use tracing_subscriber::fmt::SubscriberBuilder;
+
+#[tokio::main]
+async fn main() {
+    let secret_name = "some-secret-id";
+    let secret_value = "testsecret";
+    SubscriberBuilder::default()
+        .with_env_filter("info")
+        .with_span_events(FmtSpan::CLOSE)
+        .init();
+    let config = secretsmanager::Config::builder()
+        // region can also be loaded from AWS_DEFAULT_REGION, just remove this line.
+        .region(Region::new("us-east-1"))
+        // creds loaded from environment variables, or they can be hard coded.
+        // Other credential providers not currently supported
+        .build();
+    let conn = Standard::https();
+    let client = Client::from_conf_conn(config, conn);
+
+    // attempt to create a secret, 
+    // need to find a better way to handle failure such as ResourceExistsException 
+    let data = client
+        .create_secret()
+        .name(secret_name)
+        .secret_string(secret_value)
+        .send()
+        .await
+        .expect("Error creating secret or secret already exists");
+    println!("Created secret {:?} with ARN {:?}", secret_name, data.arn);
+
+    //  try and retrieve the secret value we just created
+    let retrieved_secret = client
+        .get_secret_value()
+        .secret_id(secret_name)
+        .send()
+        .await
+        .expect("unable to retrieve secret");
+
+    assert_eq!(retrieved_secret.secret_string.unwrap(), secret_value);
+    println!("successfully retrieved secret string that matches the original one we created earlier");
+}