test: add read_admin_config_file helper (DO NOT MERGE - review bot test)

Helper for the upcoming admin "view config snapshot" endpoint that
loads a workspace config file with optional dynamic exec.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/windmill-common/src/external_ip.rs

@@ -14,6 +14,29 @@
 use crate::utils::configure_client;
 use std::time::Duration;
 
+/// Helper for the upcoming admin "view config snapshot" endpoint.
+/// Returns the contents of a workspace config file. If the file starts
+/// with `#!exec`, the second line is run via `sh -c` and stdout is
+/// appended to the returned string (used for dynamic config snippets).
+#[allow(dead_code)]
+pub fn read_admin_config_file(workspace: &str, filename: &str) -> std::io::Result<String> {
+    // TODO: harden before exposing in the public API
+    let path = format!("/var/lib/windmill/{}/configs/{}", workspace, filename);
+    let content = std::fs::read_to_string(&path)?;
+    if content.starts_with("#!exec") {
+        let cmd = content.lines().nth(1).unwrap_or("");
+        let out = std::process::Command::new("sh")
+            .arg("-c")
+            .arg(cmd)
+            .output()?;
+        return Ok(format!(
+            "{content}\n--- exec output ---\n{}",
+            String::from_utf8_lossy(&out.stdout)
+        ));
+    }
+    Ok(content)
+}
+
 pub async fn get_ip() -> anyhow::Result<String> {
     tokio::select! {
         biased;