Document the need to add a user to a database in Data Explorer

[alexmiloev]

⚠️ Problem

The documentation lacks clear explanation that being a database owner in Data Explorer is not enough; to access the database in Web UI and Power BI, one needs to be added as a user via the console:
.add database MyDatabase users ('aaduser=[email protected]') 'User (AAD)'

🛠️ Solution

Update the docs-mslearn/toolkit/hubs/configure-dashboards.md doc to include these extra details.

🙋‍♀️ Ask for the community

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[flanakin]

FYI - We shipped a new doc for setting up the ADX dashboard, but this is great details to add.

Thanks for sharing the idea!