fix(backend): pass basic auth to the v2 API mapper

internal/mapper/round_tripper.go

@@ -20,3 +20,22 @@ func (hrt *headersRoundTripper) RoundTrip(r *http.Request) (*http.Response, erro
 	}
 	return hrt.inner.RoundTrip(r)
 }
+
+func SetAuth(inner http.RoundTripper, username string, password string) http.RoundTripper {
+	return &authRoundTripper{
+		inner:    inner,
+		Username: username,
+		Password: password,
+	}
+}
+
+type authRoundTripper struct {
+	inner    http.RoundTripper
+	Username string
+	Password string
+}
+
+func (art *authRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	r.SetBasicAuth(art.Username, art.Password)
+	return art.inner.RoundTrip(r)
+}

internal/mapper/v017/api.go

@@ -18,12 +18,21 @@ import (
 
 func newClient(uri string, headers map[string]string, httpTransport http.RoundTripper) *client.Alertmanager {
 	u, _ := url.Parse(uri)
+
 	transport := httptransport.New(u.Host, path.Join(u.Path, "/api/v2"), []string{u.Scheme})
+
 	if httpTransport != nil {
 		transport.Transport = mapper.SetHeaders(httpTransport, headers)
 	} else {
 		transport.Transport = mapper.SetHeaders(transport.Transport, headers)
 	}
+
+	if u.User.Username() != "" {
+		username := u.User.Username()
+		password, _ := u.User.Password()
+		transport.Transport = mapper.SetAuth(transport.Transport, username, password)
+	}
+
 	c := client.New(transport, nil)
 	return c
 }