Add adapter metrics types.go file

adapter/pkg/metrics/types.go

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2023, WSO2 LLC. (https://www.wso2.com)
+ *
+ * WSO2 LLC. licenses this file to you under the Apache License,
+ * Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package metrics
+
+const (
+	// PrometheusMetricType prometheus metric type
+	PrometheusMetricType = "prometheus"
+)