Alerting: API to create extra Alertmanager configurations (#106904)

What is this feature?

Implements the POST endpoint for deleting imported Mimir Alertmanager configurations:

    POST /api/convert/api/v1/alerts

The API endpoint creates the extra Alertmanager configuration with the provided identifier and matchers.

pkg/tests/api/alerting/testing.go

@@ -1262,6 +1262,92 @@ func (a apiClient) ConvertPrometheusDeleteNamespace(t *testing.T, namespaceTitle
 	requireStatusCode(t, http.StatusAccepted, status, raw)
 }
 
+func (a apiClient) ConvertPrometheusPostAlertmanagerConfig(t *testing.T, amCfg apimodels.AlertmanagerUserConfig, headers map[string]string) apimodels.ConvertPrometheusResponse {
+	t.Helper()
+
+	resp, status, body := a.RawConvertPrometheusPostAlertmanagerConfig(t, amCfg, headers)
+	requireStatusCode(t, http.StatusAccepted, status, body)
+
+	return resp
+}
+
+func (a apiClient) RawConvertPrometheusPostAlertmanagerConfig(t *testing.T, amCfg apimodels.AlertmanagerUserConfig, headers map[string]string) (apimodels.ConvertPrometheusResponse, int, string) {
+	t.Helper()
+
+	path := "%s/api/convert/api/v1/alerts"
+
+	// Based on the content-type header, marshal the data to JSON or YAML
+	contentType := headers["Content-Type"]
+	var data []byte
+	var err error
+	if contentType == "application/json" {
+		data, err = json.Marshal(amCfg)
+		require.NoError(t, err)
+	} else {
+		data, err = yaml.Marshal(amCfg)
+		require.NoError(t, err)
+	}
+
+	buf := bytes.NewReader(data)
+
+	req, err := http.NewRequest(http.MethodPost, fmt.Sprintf(path, a.url), buf)
+	require.NoError(t, err)
+
+	for key, value := range headers {
+		req.Header.Set(key, value)
+	}
+
+	return sendRequestJSON[apimodels.ConvertPrometheusResponse](t, req, http.StatusAccepted)
+}
+
+func (a apiClient) ConvertPrometheusGetAlertmanagerConfig(t *testing.T, headers map[string]string) apimodels.AlertmanagerUserConfig {
+	t.Helper()
+
+	config, status, raw := a.RawConvertPrometheusGetAlertmanagerConfig(t, headers)
+	requireStatusCode(t, http.StatusOK, status, raw)
+
+	return config
+}
+
+func (a apiClient) RawConvertPrometheusGetAlertmanagerConfig(t *testing.T, headers map[string]string) (apimodels.AlertmanagerUserConfig, int, string) {
+	t.Helper()
+
+	path := "%s/api/convert/api/v1/alerts"
+
+	req, err := http.NewRequest(http.MethodGet, fmt.Sprintf(path, a.url), nil)
+	require.NoError(t, err)
+
+	for key, value := range headers {
+		req.Header.Set(key, value)
+	}
+
+	config, status, raw := sendRequestYAML[apimodels.AlertmanagerUserConfig](t, req, http.StatusOK)
+
+	return config, status, raw
+}
+
+func (a apiClient) ConvertPrometheusDeleteAlertmanagerConfig(t *testing.T, headers map[string]string) {
+	t.Helper()
+
+	_, status, raw := a.RawConvertPrometheusDeleteAlertmanagerConfig(t, headers)
+	requireStatusCode(t, http.StatusAccepted, status, raw)
+}
+
+func (a apiClient) RawConvertPrometheusDeleteAlertmanagerConfig(t *testing.T, headers map[string]string) (apimodels.ConvertPrometheusResponse, int, string) {
+	t.Helper()
+
+	path := "%s/api/convert/api/v1/alerts"
+
+	req, err := http.NewRequest(http.MethodDelete, fmt.Sprintf(path, a.url), nil)
+	require.NoError(t, err)
+
+	for key, value := range headers {
+		req.Header.Set(key, value)
+	}
+
+	return sendRequestJSON[apimodels.ConvertPrometheusResponse](t, req, http.StatusAccepted)
+}
+
 func (a apiClient) RawConvertPrometheusDeleteNamespace(t *testing.T, namespaceTitle string, headers map[string]string) (apimodels.ConvertPrometheusResponse, int, string) {
 	t.Helper()