Support for parameter templates

[nonsocode]

There are situations when composing bicep files where a parent bicep module might want to pass parameters to a child module. In these situations, the same parameters have to be defined in the parent bicep and child bicep.

// parent.bicep
@allowedValues([
  'yes'
  'no'
  'maybe'
])
param answer string

module child './child.bicep' = {
  name: 'child'
  parameters: {
    answer: answer
  }
}

//---------------------------------------
// child.bicep
//---------------------------------------
@allowedValues([
  'yes'
  'no'
  'maybe'
])
param answer string

resource myResource 'Microsoft.Contoso/foo@2024-01-01' = {
  ...
}

Having a parameter template that can be used across both files would improve the authoring experience

e.g

//------------------
// utils.bicep
//------------------
@allowedValues([
  'yes'
  'no'
  'maybe'
])
@export()
param answer string

//----------------------------
// parent.bicep
//----------------------------
import * as utils from './utils'

module child './child.bicep' = {
  name: 'child'
  parameters: {
    // usage implies parameter declaration in this file (parent.bicep).
    // maybe having explicit pattern might be better?
    answer: utils.answer 
  }
}

//---------------------------------------
// child.bicep
//---------------------------------------
import * as utils from './utils'

resource myResource 'Microsoft.Contoso/foo@2024-01-01' = {
  properties: {
    something: utils.answer
  }
}