feat: add agent module with Nginx service commands and routes

- Introduced a new agent module with commands for managing Nginx configurations.
- Implemented `NginxService` for handling reload, validation, and configuration writing.
- Added routes for status, validation, and configuration writing using Axum.
- Created necessary command files: `reload.rs`, `run.rs`, `validate.rs`, `write_config.rs`.
- Updated `Cargo.toml` and `Cargo.lock` to include new dependencies.
- Added `.gitignore` for the agent module.
- Updated `justfile` to include OpenAPI generation for the agent.

apps/agent/src/commands/run.rs

@@ -0,0 +1,85 @@
+use std::time::Duration;
+
+use tokio::{process::Command, time::timeout};
+use tracing::error;
+
+pub fn to_file_name(
+    config_name: &str,
+    timestamp: u64,
+) -> Result<String, Box<dyn std::error::Error + Send + Sync>> {
+    // reject empty or unsafe names to avoid path traversal or invalid filesystem chars
+    if config_name.is_empty() {
+        return Err("config_name is empty".into());
+    }
+    if config_name.len() > 255 {
+        return Err("config_name too long".into());
+    }
+    if config_name.contains('/') || config_name.contains('\\') || config_name.contains("..") {
+        return Err("config_name contains invalid path characters".into());
+    }
+    if !config_name
+        .chars()
+        .all(|c| c.is_ascii_alphanumeric() || "-._".contains(c))
+    {
+        return Err("config_name contains invalid characters".into());
+    }
+
+    Ok(format!("{}_{}.conf", timestamp, config_name))
+}
+
+pub async fn run_cmd(
+    cmd: &str,
+    args: &[&str],
+    dur_s: u64,
+) -> Result<(i32, String), Box<dyn std::error::Error + Send + Sync>> {
+    let mut c = Command::new(cmd);
+    c.args(args);
+    let res = timeout(Duration::from_secs(dur_s), c.output()).await;
+    let out = match res {
+        Ok(Ok(out)) => out,
+        Ok(Err(e)) => return Err(Box::new(e)),
+        Err(_) => {
+            return Err(Box::new(std::io::Error::new(
+                std::io::ErrorKind::TimedOut,
+                "command timeout",
+            )));
+        }
+    };
+    let code = out.status.code().unwrap_or(-1);
+    let output = String::from_utf8_lossy(&[out.stdout, out.stderr].concat()).to_string();
+    if code != 0 {
+        error!("command failed ({}): {}", code, output);
+        return Err(format!("command failed ({}): {}", code, output).into());
+    }
+    Ok((code, output))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::to_file_name;
+
+    #[test]
+    fn to_file_name_valid() {
+        let res = to_file_name("myconf", 1234).expect("should succeed");
+        assert_eq!(res, "1234_myconf.conf");
+    }
+
+    #[test]
+    fn to_file_name_empty() {
+        assert!(to_file_name("", 1).is_err());
+    }
+
+    #[test]
+    fn to_file_name_invalid_chars() {
+        assert!(to_file_name("bad/name", 1).is_err());
+        assert!(to_file_name("bad\\name", 1).is_err());
+        assert!(to_file_name("bad..name", 1).is_err());
+        assert!(to_file_name("bad$name", 1).is_err());
+    }
+
+    #[test]
+    fn to_file_name_too_long() {
+        let long = "a".repeat(300);
+        assert!(to_file_name(&long, 1).is_err());
+    }
+}