[mattermost] Add Support of Dashboard

[mohitjha-elastic]

Proposed Commit Message

mattermost: add support of dashboard.

Currently, the integration does not include the support of dashboard hence added audit dashboard
in the integration to get better visualization of the data.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

How to test this PR locally

Clone integrations repo.
Install the elastic package locally.
Start the elastic stack using the elastic package.
Move to integrations/packages/mattermost directory.
Run the following command to run tests.
elastic-package test -v

Related issues

• Part of SSI Integration: Missing Dashboard #13702
• Part of Security Integrations | Missing Dashboards #3102

Screenshots

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)

[elastic-vault-github-plugin-prod]

🚀 Benchmarks report

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[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 5354093

cc @mohitjha-elastic

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
99.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube