v0.35.1: performance, AGPL licensing and documentation overhaul

- Web Server reads static files inline; proxy middleware chain flattened
- About window with license summary and project links; AGPL-3.0-or-later
- Rewritten documentation: feature list, screenshots, performance guide
- Fix false spikes in per-Vhost request-rate charts

src/cache/lookup/tiered.rs

@@ -22,9 +22,9 @@ impl Cache {
         if cached.body.len() > settings.max_object_bytes {
             return None;
         }
-        if !headers.contains_key("date") {
+        if !headers.contains_key(::http::header::DATE) {
             if let Ok(value) = httpdate::fmt_http_date(SystemTime::now()).parse() {
-                headers.insert("date", value);
+                headers.insert(::http::header::DATE, value);
             }
         }
         headers.remove("x-request-id");
@@ -34,11 +34,11 @@ impl Cache {
         let vary = plan.vary.clone();
         let tags = cache_tags(&headers);
         let origin_etag = validation_headers
-            .get("etag")
+            .get(::http::header::ETAG)
             .cloned()
             .or_else(|| cached.origin_etag.clone());
         let origin_last_modified = validation_headers
-            .get("last-modified")
+            .get(::http::header::LAST_MODIFIED)
             .cloned()
             .or_else(|| cached.origin_last_modified.clone());
         let cost = hot_entry_cost(
@@ -98,8 +98,7 @@ impl Cache {
         }
         self.counters.hits.fetch_add(1, Ordering::Relaxed);
         let mut response = cached.response(headers);
-        response.headers_mut().insert(
-            "age",
+        response.headers_mut().insert(::http::header::AGE,
             HeaderValue::from_str(&age.to_string()).expect("integer header"),
         );
         Some(Hit {
@@ -156,11 +155,11 @@ impl Cache {
             .cloned();
         let origin_etag = match origin_validators.as_ref() {
             Some(validators) => validators.etag.clone(),
-            None => headers.get("etag").cloned(),
+            None => headers.get(::http::header::ETAG).cloned(),
         };
         let origin_last_modified = match origin_validators.as_ref() {
             Some(validators) => validators.last_modified.clone(),
-            None => headers.get("last-modified").cloned(),
+            None => headers.get(::http::header::LAST_MODIFIED).cloned(),
         };
         let transformed = parts
             .extensions