api: Add the metrics.json Swagger file

This patch adds the swagger definition for the metrics API.

Currently, the API defines a get and set of the metric_relabel_config.

api/api-doc/metrics.def.json

@@ -0,0 +1,34 @@
+    "metrics_config": {
+        "id": "metrics_config",
+        "summary": "An entry in the metrics configuration",
+        "properties": {
+            "source_labels": {
+                "type": "array",
+                "items": {
+                    "type": "string"
+                },
+                "description": "The source labels, a match is based on concatination of the labels"
+            },
+            "action": {
+                "type": "string",
+                "description": "The action to perfrom on match",
+                "enum": ["skip_when_empty", "report_when_empty", "replace", "keep", "drop", "drop_label"]
+            },
+            "target_label": {
+                "type": "string",
+                "description": "The application state version"
+            },
+            "replacement": {
+                "type": "string",
+                "description": "The replacement string to use when replacing a value"
+            },
+            "regex": {
+                "type": "string",
+                "description": "The regex string to use when replacing a value"
+            },
+            "separator": {
+                "type": "string",
+                "description": "The separator string to use when concatinating the labels"
+            }
+        }
+    }

api/api-doc/metrics.json

@@ -0,0 +1,66 @@
+    "/v2/metrics-config/":{
+        "get":{
+            "description":"Return the metrics layer configuration",
+            "operationId":"get_metrics_config",
+            "produces":[
+                "application/json"
+            ],
+            "tags":[
+                "metrics"
+            ],
+            "parameters":[
+            ],
+            "responses":{
+                "200":{
+                "schema": {
+                    "type":"array",
+                    "items":{
+                        "$ref":"#/definitions/metrics_config",
+                        "description":"metrics Config value"
+                    }
+                    }
+                },
+                "default":{
+                    "description":"unexpected error",
+                    "schema":{
+                        "$ref":"#/definitions/ErrorModel"
+                    }
+                }
+            }
+        },
+        "post": {
+             "description":"Set the metrics layer relabel configuration",
+            "operationId":"set_metrics_config",
+            "produces":[
+                "application/json"
+            ],
+            "tags":[
+                "metrics"
+            ],
+            "parameters":[
+               {
+                "in":"body",
+                "name":"conf",
+                "description":"An array of relabel_config objects",
+                "schema": {
+                    "type":"array",
+                    "items":{
+                        "$ref":"#/definitions/metrics_config",
+                        "description":"metrics Config value"
+                    }
+                }
+               }
+            ],
+            "responses":{
+                "200":{
+                    "description": "OK"
+                },
+                "default":{
+                    "description":"unexpected error",
+                    "schema":{
+                        "$ref":"#/definitions/ErrorModel"
+                    }
+                }
+            }
+        }
+    }

configure.py

@@ -1140,6 +1140,7 @@ api = ['api/api.cc',
        'api/task_manager_test.cc',
        'api/config.cc',
        Json2Code('api/api-doc/config.json'),
+       Json2Code('api/api-doc/metrics.json'),
        'api/error_injection.cc',
        Json2Code('api/api-doc/error_injection.json'),
        'api/authorization_cache.cc',