[LBSD-2786] - Complete Instance Settings UI

[eos87]

Purpose

Completes the implementation of the UI to manage Instance Settings. This UI is restricted only to users that have the is_support attribute active. If the attribute is not active, then the UI is not visible.

What has changed

• The resource schema has been enhanced
• Validator method has been removed in favour of using Cerberus (Python Eve) dependency to run the validations against the resource's schema
• Improved service class to make the instance settings act as a singleton
• Implemented a few edge case when settings are not present
• Improved frontend controller and fixed linter issues
• Removed Instance Admin role in favour of using is_support attribute instead
• Render instance settings UI based on user's is_support attribute
• Added validation in the backend side so user cannot modify the instance settings if it doesn't have the is_support enabled
• Remove the merge_config method to keep it simple for now. In the future we can analyse if a more complex approach is needed
• Adjusted couple of places with new features service (I've missed them in previous PR)
• Adjusted tests

Steps to test

• Checkout the branch
• Run the services
• Go to instance settings UI. Notice that if user is not support, the menu entry will not render. Otherwise it should
• Try to save the setting and play with validations. The settings structure should look like this below. You can try removing "features" for example, and the system should catch that.

{
    "settings": {
        "solo": {
            "features": {
                "syndication": true,
                "marketplace": false,
                "theme_styles": false,
                "custom_themes": false,
                "change_blog_theme": false,
                "freetypes_manager": false,
                "archived_blogs_available": false
            },
            "limits": {
                "blogs": 1,
                "themes": 1,
                "blog_members": 1,
                "custom_themes": 0
            }
        },
        "team": {
            "features": {
                "syndication": true,
                "marketplace": true,
                "theme_styles": true,
                "custom_themes": true,
                "change_blog_theme": true,
                "freetypes_manager": true,
                "archived_blogs_available": true
            },
            "limits": {
                "blogs": 3,
                "themes": 6,
                "blog_members": 5,
                "custom_themes": 5
            }
        }
    }
}

Thanks for reviewing!

Resolves: LBSD-2786

[BrianMwangi21]

I've tested it locally and it works. LGTM! 👍

[eos87]

I will merge this although there will be another PR just to adjust the plans' names and features/limits (Liveblog Go and Uni)