Set default_home_dashboard_path on grafana resource deployment

[gruberdev]

[Feature Request]

Description

• On the API reference documentation for configuring the operator objects there's one configuration option at grafana.spec.config.dashboards you'll notice that it differs from the official documentation as it is missing the item default_home_dashboard_path (ref).
• The item missing allows for the configuration of a default dashboard for all users of that grafana resource object, and even though there is official documentation on how to change this configuration in a discrete manner, grafana-operator's equivalent documentation does not cite any other alternative to provision this same configuration other than using folders, which do not achieve the same functionality.

Suggested change:

• An option grafana.spec.config.dashboards.default_home_dashboard_path to define the base path used to configure the dashboard

Alternative solutions until now

• Rebuilding the operator to use the Grafana container in a way that pulls a pre-built image with a .json dashboard already placed at the correct location
• Using custom volumes to override the file's location at /usr/share/grafana/public/dashboards/home.json
• Overriding the configuration of grafana.ini to point towards another location (a remote volume for ex.) in case the second solution doesn't work

[NissesSenap]

Thanks for the PR @Bobbins228 🥇

[ninkaninus]

Thanks a lot for this PR @gruberdev

I am struggling a bit with locating where my dashboards is provisioned (they are created from a URL in grafanadashboard resource).
But I am unable to find the path to them in the container, so where did you locate yours?