http tap: add request/response trailer matching (#5804)

1) Add request/response trailer matching
2) Output request/response trailers
3) Refactor matchers to reduce boilerplate and make it harder
   to make mistakes when adding new update functions.
4) Split out a match configuration for HTTP request and response
   into individual things like request headers, request trailers,
   etc. This will make it easier and more logical to add various
   types of body matching and wire it up using the existing and/or
   logic.

Signed-off-by: Matt Klein <mklein@lyft.com>

Mirrored from https://github.com/envoyproxy/envoy @ fbcf6bcaac6ac3c2b13f8c51fb1470a25b240abd

envoy/data/tap/v2alpha/http.proto

@@ -9,9 +9,18 @@ import "envoy/api/v2/core/base.proto";
 
 // A fully buffered HTTP trace message.
 message HttpBufferedTrace {
-  // Request headers.
+  // HTTP message wrapper.
-  repeated api.v2.core.HeaderValue request_headers = 2;
+  message Message {
+    // Message headers.
+    repeated api.v2.core.HeaderValue headers = 1;
 
-  // Response headers.
+    // Message trailers.
-  repeated api.v2.core.HeaderValue response_headers = 3;
+    repeated api.v2.core.HeaderValue trailers = 2;
+  }
+
+  // Request message.
+  Message request = 1;
+
+  // Response message.
+  Message response = 2;
 }

envoy/service/tap/v2alpha/common.proto

@@ -48,23 +48,23 @@ message MatchPredicate {
     // The match configuration will always match.
     bool any_match = 4 [(validate.rules).bool.const = true];
 
-    // HTTP request match configuration.
+    // HTTP request headers match configuration.
-    HttpRequestMatch http_request_match = 5;
+    HttpHeadersMatch http_request_headers_match = 5;
 
-    // HTTP response match configuration.
+    // HTTP request trailers match configuration.
-    HttpResponseMatch http_response_match = 6;
+    HttpHeadersMatch http_request_trailers_match = 6;
-  }
-}
 
-// HTTP request match configuration.
+    // HTTP response headers match configuration.
-message HttpRequestMatch {
+    HttpHeadersMatch http_response_headers_match = 7;
-  // HTTP request headers to match.
+
-  repeated api.v2.route.HeaderMatcher headers = 1;
+    // HTTP response trailers match configuration.
+    HttpHeadersMatch http_response_trailers_match = 8;
+  }
 }
 
-// HTTP response match configuration.
+// HTTP headers match configuration.
-message HttpResponseMatch {
+message HttpHeadersMatch {
-  // HTTP response headers to match.
+  // HTTP headers to match.
   repeated api.v2.route.HeaderMatcher headers = 1;
 }