Documentation on how to use opensearch dashboards (to monitor storage)

[arlake228]

We should add some documentation on how to use opensearch-dashboard. In particular:

• How do I access the dashboard and do I need any packaged installed?
• Where do I find the credentials to login to the dashboard?
• How do I look at raw data in discover panel?
• How do I look at index storage size?

[laeti-tia]

To quickly answer the 2 first ones:

• on a perfsonar-archive installation you can access: https://archive-hostname.tld/opensearchdash/
• login credentials are stored in /etc/perfsonar/opensearch/opensearch_login