Structured queries

[goller]

• CHANGELOG.md updated
• Rebased/mergable
• Tests pass
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Connect #824

The problem

The current QueryConfig object is not able to represent InfluxQL.
Not simple to convert InfluxQL to QueryConfigs

The Solution

This PR creates /chonograf/v1/sources/:id/queries endpoint to analyze queries and give back meta database about 'em.

The routes link is available from links.queries in the source object.

The endpoint only accepts POST of the following JSON structure:

{
	"queries": [
		{
			"query": ""
		}
	]
}

and responds with:

{
  "queries": [
    {
      		"query": "",
     	 	"queryConfig": {},
     		 "queryAST": {}
		}
	]
}

The response is in the same order as the request. query in response is identical to the request.
queryConfig will always be present and either initialized with rawText if the query is not parsable, or null.

queryAST is present or not if the query can be represented with the AST.

Examples:

{
	"queries": [
		{
			"query": 	"SELECT usage_idle from telegraf.autogen.cpu"
		},
		{
			"query": 	"SELECT howdy from telegraf.autogen.doody"
		},
		{
			"query": 	"SHOW MEASUREMENTS"
		}
	]
}

It will respond with the following:

{
  "queries": [
    {
      "query": "SELECT usage_idle from telegraf.autogen.cpu",
      "queryConfig": {
        "database": "telegraf",
        "measurement": "cpu",
        "retentionPolicy": "autogen",
        "fields": [
          {
            "field": "usage_idle",
            "funcs": []
          }
        ],
        "tags": {},
        "groupBy": {
          "time": "",
          "tags": []
        },
        "areTagsAccepted": false,
        "rawText": null
      },
      "queryAST": {
        "fields": [
          {
            "column": {
              "expr": "reference",
              "val": "usage_idle"
            }
          }
        ],
        "sources": [
          {
            "database": "telegraf",
            "retentionPolicy": "autogen",
            "name": "cpu",
            "type": "measurement"
          }
        ]
      }
    },
    {
      "query": "SELECT howdy from telegraf.autogen.doody",
      "queryConfig": {
        "database": "telegraf",
        "measurement": "doody",
        "retentionPolicy": "autogen",
        "fields": [
          {
            "field": "howdy",
            "funcs": []
          }
        ],
        "tags": {},
        "groupBy": {
          "time": "",
          "tags": []
        },
        "areTagsAccepted": false,
        "rawText": null
      },
      "queryAST": {
        "fields": [
          {
            "column": {
              "expr": "reference",
              "val": "howdy"
            }
          }
        ],
        "sources": [
          {
            "database": "telegraf",
            "retentionPolicy": "autogen",
            "name": "doody",
            "type": "measurement"
          }
        ]
      }
    },
    {
      "query": "SHOW MEASUREMENTS",
      "queryConfig": {
        "database": "",
        "measurement": "",
        "retentionPolicy": "",
        "fields": [],
        "tags": {},
        "groupBy": {
          "time": "",
          "tags": []
        },
        "areTagsAccepted": false,
        "rawText": "SHOW MEASUREMENTS"
      }
    }
  ]
}