Implement config adapters and beginning of Caddyfile adapter

Along with several other changes, such as renaming caddyhttp.ServerRoute
to caddyhttp.Route, exporting some types that were not exported before,
and tweaking the caddytls TLS values to be more consistent.

Notably, we also now disable automatic cert management for names which
already have a cert (manually) loaded into the cache. These names no
longer need to be specified in the "skip_certificates" field of the
automatic HTTPS config, because they will be skipped automatically.

modules/caddyhttp/encode/encode.go

@@ -52,19 +52,15 @@ type Encode struct {
 
 // Provision provisions enc.
 func (enc *Encode) Provision(ctx caddy.Context) error {
-	enc.writerPools = make(map[string]*sync.Pool)
-
 	for modName, rawMsg := range enc.EncodingsRaw {
 		val, err := ctx.LoadModule("http.encoders."+modName, rawMsg)
 		if err != nil {
 			return fmt.Errorf("loading encoder module '%s': %v", modName, err)
 		}
-		encoder := val.(Encoding)
-
-		enc.writerPools[encoder.AcceptEncoding()] = &sync.Pool{
-			New: func() interface{} {
-				return encoder.NewEncoder()
-			},
+		encoding := val.(Encoding)
+		err = enc.addEncoding(encoding)
+		if err != nil {
+			return err
 		}
 	}
 	enc.EncodingsRaw = nil // allow GC to deallocate - TODO: Does this help?
@@ -85,10 +81,28 @@ func (enc *Encode) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyh
 		defer w.(*responseWriter).Close()
 		break
 	}
-
 	return next.ServeHTTP(w, r)
 }
 
+func (enc *Encode) addEncoding(e Encoding) error {
+	ae := e.AcceptEncoding()
+	if ae == "" {
+		return fmt.Errorf("encoder does not specify an Accept-Encoding value")
+	}
+	if _, ok := enc.writerPools[ae]; ok {
+		return fmt.Errorf("encoder already added: %s", ae)
+	}
+	if enc.writerPools == nil {
+		enc.writerPools = make(map[string]*sync.Pool)
+	}
+	enc.writerPools[ae] = &sync.Pool{
+		New: func() interface{} {
+			return e.NewEncoder()
+		},
+	}
+	return nil
+}
+
 // openResponseWriter creates a new response writer that may (or may not)
 // encode the response with encodingName. The returned response writer MUST
 // be closed after the handler completes.