Construct Template Enhancements

[DavidSeptimus-Klotho]

This PR make substantial enhancements to construct templates

Features

Interpolation enhancements

• You can mix and match go template {{}} and existing ${} interpolation syntax in construct/binding templates.
• Additionally, referencing properties containing a . is now possible using [part1.part2] syntax.

prop1: '{{ toUpper .Inputs.Input1 }}'
prop2: '${inputs:Input1}-{{ .Inputs.Input1 }}-${resources:[{{ .Inputs.Name }}]}'
prop3: '{{ if .Inputs.ReadOnly }}readonly{{ else }}readwrite{{ end }}'

Input rule enhancements

• You can now write for_each-do oriented rules (mixing for_each and if in a single rule will cause an error). The do component of the rule will be executed once for each index or entry in the item selected in the for_each go template using the .Select function.
• Resources added by input rules include a customizable prefix.
• In a for_each, rule, use the .Select function to select a value from the current interpolation context to iterate over and reference the current selection with .Selected.
• You can referenced the following within .Selected where applicable:
  • .Key
  • .Index
  • .Value

input_rules:
  - for_each: '{{ .Select "inputs.Routes" }}'
    prefix: '{{ toLower (replace `[^\w]` "-"  .Selected.Value.Path) }}'
    do:
      resources:
        ...

• Input rules now contain a rules field that enables nested rules. Nested rules inherit the prefix of their parent by default. Prefix hierarchies are merged with a . separator (e.g., MyRoute.Method)

input_rules:
  - if: {{ .Inputs.SomeBool }}
    then:
      resources:
        Resource1:
        ...
      rules:
        - for_each: {{ .Select "inputs.DependentInput" }}
          do: ...

Structured Inputs

Structured inputs are now supported using the same syntax as resource template properties. Notably, model inputs are not available and resource refs (e.g. resource:Id#property are not supported)

No validation enhancements were made to this functionality -- that will be a separate effort, so most validation declared in templates is still ignored.

Inputs:
  HeathCheck:
    type: map
    properties:
      Protocol:
        type: string
        required: true
        allowed_values:
          - TCP
          - UDP
          - HTTPS
          - HTTP
      Port:
        type: int
        default_value: 80
      Path:
        type: string
        default_value: /health