Add a replacement cli-parsing function for Opt that can be used in quickstart with no external dependencies

.bleep

@@ -1 +1 @@
-dad4171e22fa0f38c7dc19247c36f4004d1245de
+8f4c536768b4ed3720cc4a6e651d0ed519aa6a60

docs/quick_start.md

@@ -237,7 +237,7 @@ take advantage of with single-line change.
 
 ```rust
 fn main() {
-    let mut my_server = Server::new(Some(Opt::default())).unwrap();
+    let mut my_server = Server::new(Some(Opt::parse_args())).unwrap();
     ...
 }
 ```

pingora-core/src/server/configuration/mod.rs

@@ -227,6 +227,15 @@ impl ServerConf {
     }
 }
 
+/// Create an instance of Opt by parsing the current command-line args.
+/// This is equivalent to running `Opt::parse` but does not require the
+/// caller to have included the `clap::Parser`
+impl Opt {
+    pub fn parse_args() -> Self {
+        Opt::parse()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;