feat(rpc): Opt-in HTTP RPC API Authorization (#10218)

Context: https://github.com/ipfs/kubo/issues/10187
Co-authored-by: Marcin Rataj <lidel@lidel.org>

client/rpc/auth/auth.go

@@ -0,0 +1,29 @@
+package auth
+
+import "net/http"
+
+var _ http.RoundTripper = &AuthorizedRoundTripper{}
+
+type AuthorizedRoundTripper struct {
+	authorization string
+	roundTripper  http.RoundTripper
+}
+
+// NewAuthorizedRoundTripper creates a new [http.RoundTripper] that will set the
+// Authorization HTTP header with the value of [authorization]. The given [roundTripper] is
+// the base [http.RoundTripper]. If it is nil, [http.DefaultTransport] is used.
+func NewAuthorizedRoundTripper(authorization string, roundTripper http.RoundTripper) http.RoundTripper {
+	if roundTripper == nil {
+		roundTripper = http.DefaultTransport
+	}
+
+	return &AuthorizedRoundTripper{
+		authorization: authorization,
+		roundTripper:  roundTripper,
+	}
+}
+
+func (tp *AuthorizedRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	r.Header.Set("Authorization", tp.authorization)
+	return tp.roundTripper.RoundTrip(r)
+}