Add support for appinsights in the metricbeat azure module

[narph]

What does this PR do?

Adds an azure metricset that retrieves azure app insights metrics.

Why is it important?

Adds support for appinsights in the metricbeat azure module

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Closes Add support for appinsights in Metricbeat and Filebeat #18570

Using the app insights GET metrics API (https://dev.applicationinsights.io/documentation/Using-the-API/Metrics) users can collect specified metrics.
This metricset can be followed by a light metricset that will collect the most relevant/popular app metrics and dashboards.

Configuration:

- module: azure
  metricsets:
    - app_insights
  enabled: true
  period: 2h
  application_id: ""
  api_key: ""
  metrics:
    - id: ["requests/count", "requests/failed"]
      segment: "request/name"
      aggregation: ["sum"]

Example output:

{
    "@timestamp": "2017-10-12T08:05:34.853Z",
        "azure" : {
        "app_insights" : {
            "metrics" : {
                "requests_failed" : {
                    "sum" : 182
                },
                "request_name" : "GET /favicon.ico"
            },
            "start_date" : "2020-07-12T10:52:11.831Z",
            "end_date" : "2020-07-12T12:52:11.831Z",
            "application_id" : "42cb59a9-d5be-400b-a5c4-69b0a0026ac6"
        }
    },
    "cloud": {
        "provider": "azure"
    },
    "event": {
        "dataset": "azure.app_insights",
        "duration": 115000,
        "module": "azure"
    },
    "metricset": {
        "name": "app_insights",
        "period": 10000
    },
    "service": {
        "type": "azure"
    }
}

[elasticmachine]

💚 Build Succeeded

Expand to view the summary

Build stats

• Build Cause: [Pull request #18940 updated]

• Start Time: 2020-07-13T15:44:18.810+0000

• Duration: 64 min 54 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3454
Skipped	793
Total	4247

Steps errors

Expand to view the steps failures

• Name: Report to Codecov

  • Description: curl -sSLo codecov https://codecov.io/bash for i in auditbeat filebeat heartbeat libbeat metricbeat packetbeat winlogbeat journalbeat do FILE="${i}/build/coverage/full.cov" if [ -f "${FILE}" ]; then bash codecov -f "${FILE}" fi done

  • Duration: 2 min 22 sec

  • Start Time: 2020-07-13T16:10:36.696+0000

  • log

• Name: Report to Codecov

  • Description: curl -sSLo codecov https://codecov.io/bash for i in auditbeat filebeat heartbeat libbeat metricbeat packetbeat winlogbeat journalbeat do FILE="${i}/build/coverage/full.cov" if [ -f "${FILE}" ]; then bash codecov -f "${FILE}" fi done

  • Duration: 1 min 27 sec

  • Start Time: 2020-07-13T16:37:29.228+0000

  • log

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)