[Docs] Providing an example for the validate command (#487)

* providing a getting started example of how to use the validate command from the library

* cleanup

Cargo.toml

@@ -3,5 +3,6 @@
 members = [
     "guard",
     "guard-lambda",
-    "guard-ffi"
+    "guard-ffi",
+    "guard-examples/library"
 ]

guard-examples/library/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "library"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+cfn-guard = { version = "3.1.0-beta", path = "../../guard" }
+anyhow = "1.0.81"

guard-examples/library/src/main.rs

@@ -0,0 +1,43 @@
+use std::io::Cursor;
+
+use anyhow::Context;
+use cfn_guard::{
+    commands::{
+        validate::{OutputFormatType, ShowSummaryType},
+        Executable,
+    },
+    utils::{
+        reader::{ReadBuffer, Reader},
+        writer::{WriteBuffer, Writer},
+    },
+    CommandBuilder, ValidateBuilder,
+};
+
+#[derive(Debug)]
+pub struct Payload {
+    pub data: String,
+    pub rules: Vec<String>,
+}
+
+fn main() -> anyhow::Result<()> {
+    let payload = r#"{"data": ["{\"Resources\":{\"NewVolume\":{\"Type\":\"AWS::EC2::Volume\",\"Properties\":{\"Size\":500,\"Encrypted\":false,\"AvailabilityZone\":\"us-west-2b\"}},\"NewVolume2\":{\"Type\":\"AWS::EC2::Volume\",\"Properties\":{\"Size\":50,\"Encrypted\":false,\"AvailabilityZone\":\"us-west-2c\"}}},\"Parameters\":{\"InstanceName\":\"TestInstance\"}}","{\"Resources\":{\"NewVolume\":{\"Type\":\"AWS::EC2::Volume\",\"Properties\":{\"Size\":500,\"Encrypted\":false,\"AvailabilityZone\":\"us-west-2b\"}},\"NewVolume2\":{\"Type\":\"AWS::EC2::Volume\",\"Properties\":{\"Size\":50,\"Encrypted\":false,\"AvailabilityZone\":\"us-west-2c\"}}},\"Parameters\":{\"InstanceName\":\"TestInstance\"}}"], "rules" : [ "Parameters.InstanceName == \"TestInstance\"","Parameters.InstanceName == \"TestInstance\"" ]}"#;
+    let mut reader = Reader::new(ReadBuffer::Cursor(Cursor::new(Vec::from(
+        payload.as_bytes(),
+    ))));
+    let mut writer = Writer::new_with_err(WriteBuffer::Vec(vec![]), WriteBuffer::Vec(vec![]));
+
+    let cmd = ValidateBuilder::default()
+        .payload(true)
+        .output_format(OutputFormatType::JSON)
+        .structured(true)
+        .show_summary(vec![ShowSummaryType::None])
+        .try_build()
+        .context("failed to build validate command")?;
+
+    cmd.execute(&mut writer, &mut reader)?;
+
+    let content = writer.stripped().context("failed to read from writer")?;
+    println!("{content}");
+
+    Ok(())
+}