support upgrade-insecure-requests option

src/backend_opt.rs

@@ -3,6 +3,7 @@ use crate::error::*;
 #[derive(Debug, Clone, Hash, Eq, PartialEq)]
 pub enum UpstreamOption {
   OverrideHost,
+  UpgradeInsecureRequests,
   // TODO: Adds more options for heder override
 }
 impl TryFrom<&str> for UpstreamOption {
@@ -10,6 +11,7 @@ impl TryFrom<&str> for UpstreamOption {
   fn try_from(val: &str) -> Result<Self> {
     match val {
       "override_host" => Ok(Self::OverrideHost),
+      "upgrade_insecure_requests" => Ok(Self::UpgradeInsecureRequests),
       _ => Err(anyhow!("Unsupported header option")),
     }
   }