DTOSS-11637: Add a shared dashboard module

[Harriethw]

Description

We would like to setup a dashboard on the Azure portal for our different environments on the Invite team.

This would allow repos to pass in a template file as the dashboard_properties, e.g:

  dashboard_properties = templatefile("dashboard-template.tpl",
      {
        environment = var.environment
        sub_id      = var.hub_subscription_id
      }
    )

https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/portal_dashboard

To see an example of a use case, I have a WIP branch here. https://github.com/NHSDigital/dtos-manage-breast-screening/compare/DTOSS-11637-dashboard-terraform?expand=1

Context

Add's a shared context for Dashboards, means we can start version controlling the content.

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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