Remove secret file existence check in Validate for headers

This commit removes the check for the existence of the secret file for
headers in the `Validate` function. The check is not valid for relative
paths since `Validate` is called before `SetDirectory`, which is
responsible for setting up the environment. This change aligns with the
handling of other secret files, which are not checked during config
validation.

Signed-off-by: Julien <roidelapluie@o11y.eu>

config/headers.go

@@ -78,17 +78,10 @@ func (h *Headers) SetDirectory(dir string) {
 
 // Validate validates the Headers config.
 func (h *Headers) Validate() error {
-	for n, header := range h.Headers {
+	for n := range h.Headers {
 		if _, ok := reservedHeaders[http.CanonicalHeaderKey(n)]; ok {
 			return fmt.Errorf("setting header %q is not allowed", http.CanonicalHeaderKey(n))
 		}
-		for _, v := range header.Files {
-			f := JoinDir(h.dir, v)
-			_, err := os.ReadFile(f)
-			if err != nil {
-				return fmt.Errorf("unable to read header %q from file %s: %w", http.CanonicalHeaderKey(n), f, err)
-			}
-		}
 	}
 	return nil
 }

config/http_config.go

@@ -828,7 +828,7 @@ type basicAuthRoundTripper struct {
 
 // NewBasicAuthRoundTripper will apply a BASIC auth authorization header to a request unless it has
 // already been set.
-func NewBasicAuthRoundTripper(username SecretReader, password SecretReader, rt http.RoundTripper) http.RoundTripper {
+func NewBasicAuthRoundTripper(username, password SecretReader, rt http.RoundTripper) http.RoundTripper {
 	return &basicAuthRoundTripper{username, password, rt}
 }
 

config/http_config_test.go

@@ -1107,7 +1107,7 @@ func getCertificateBlobs(t *testing.T) map[string][]byte {
 	return bs
 }
 
-func writeCertificate(bs map[string][]byte, src string, dst string) {
+func writeCertificate(bs map[string][]byte, src, dst string) {
 	b, ok := bs[src]
 	if !ok {
 		panic(fmt.Sprintf("Couldn't find %q in bs", src))