feat(dashboard): opening dashboard to extension

[StefanZuefeldt]

adds 'templates' and 'extensions' to dashboard config templates: table of functions that build sections

• the 'built-in' sections are considered templates extensions: array of collections of templates and formats
• intention is for a low-hassle way to include templates and formats from plugins

formats will now respect custom format fields, and not just custom formats over the built-in fields

Description

A good-faith attempt to make extending the Dashboard more convenient. Constructive feedback and changes are welcome.

The overall goal:

• Develop plugins that can provide new dashboard behaviors
• Users able to apply plugin behavior to the dashboard with minimal effort
• Prefer a declarative approach

This is accomplished with the following:

• A templates table is added to configuration
  • By default, populated with all of the 'built-in sections'
  • Users may add more templates
  • Previous capabilities would require users to alter the modules' sections table to add new 'built-in sections'. This probably wasn't recommended, either.
• The formats table will now support arbitrary field names
  • Previous format support only permitted changing the built-in formats / fields
• Formats as functions can now be passed as a table with an align value, and a priority value.
  • align='left' will act as icon formats
  • align='right' will act as key/label formats
• The opts table of format functions now also provides the dashboard instance, under the name dashboard
  • This can permit a format to call another format and modify its results
• An extensions array is added to configuration, to support single-line plugin extension
  • Array of either tables, or functions that return tables
  • Provides new templates and formats
• e.g.

  {
    extensions = {
      {
        templates = {
          hello_world = function(item)
            if type(item.planet) == 'string' then
              return { greeting = 'Hello ' .. item.planet }
            else
              return { greeting = 'Hello World' }
            end
          end
        },
        formats = {
          greeting = function(item, opts)
            return { item.greeting, hl = 'markdownH5' }
          end
        }
      },
    },
    sections = {
      { section = 'header' },
      { section = 'hello_world', planet = 'Moon' },
      { section = 'hello_world', planet = 'Sun' },
    }
  }

• However, the more intended way to use extensions would be as below:

  {
    extensions = {
      function() return require('hello-world-dashboard').extension end
    },
    sections = {
      { section = 'header' },
      { section = 'hello_world', planet = 'Moon' },
      { section = 'hello_world', planet = 'Sun' },
    }
  }

• Users developing local templates or formats would be expected to use templates and the existing formats tables
• Users loading templates and formats from plugins would be expected to use the extensions array

Related Issue(s)

Screenshots

Hello world demo