feat: support customized header to metadata processor (#2162)

* chore: add more tests

* feat: support customized header processor

gateway/internal/headerprocessor.go

@@ -11,8 +11,8 @@ const (
 	metadataPrefix       = "gateway-"
 )
 
-// BuildHeaders builds the headers for the gateway from HTTP headers.
-func BuildHeaders(header http.Header) []string {
+// ProcessHeaders builds the headers for the gateway from HTTP headers.
+func ProcessHeaders(header http.Header) []string {
 	var headers []string
 
 	for k, v := range header {

gateway/internal/headerprocessor_test.go

@@ -10,12 +10,12 @@ import (
 func TestBuildHeadersNoValue(t *testing.T) {
 	req := httptest.NewRequest("GET", "/", nil)
 	req.Header.Add("a", "b")
-	assert.Nil(t, BuildHeaders(req.Header))
+	assert.Nil(t, ProcessHeaders(req.Header))
 }
 
 func TestBuildHeadersWithValues(t *testing.T) {
 	req := httptest.NewRequest("GET", "/", nil)
 	req.Header.Add("grpc-metadata-a", "b")
 	req.Header.Add("grpc-metadata-b", "b")
-	assert.EqualValues(t, []string{"gateway-A:b", "gateway-B:b"}, BuildHeaders(req.Header))
+	assert.ElementsMatch(t, []string{"gateway-A:b", "gateway-B:b"}, ProcessHeaders(req.Header))
 }