Cannot use a symbolic name of Microsoft.Management/managementGroups as scope of an MG module

[majastrz]

Bicep version
Latest in main

Describe the bug
We allow a resource of type Microsoft.Resources/resourceGroup to be used as a scope of an RG module. We should support using a resources of type Microsoft.Management/managementGroups as scopes of MG modules.

Currently, the error you get is the following:
Scope "resource" is not valid for this module. Permitted scopes: "managementGroup".

To Reproduce
main.bicep:

targetScope = 'tenant'

param mainMgName string
param managementGroups array

resource mainMg 'Microsoft.Management/managementGroups@2020-05-01' = {
  name: mainMgName
}

resource mgs 'Microsoft.Management/managementGroups@2020-05-01' = [for (mg, i) in managementGroups: {
  name: mg
}]

module singleMgModule 'modules/managementGroup.bicep' = {
  name: 'single-mg'
  scope: mainMg
}

managementGroup.bicep:

targetScope = 'managementGroup'

Additional context
Add any other context about the problem here.

[anthony-c-martin]

Some implementation info - here's where we do this for resourceGroup resources. I expect it should be straightforward to do the same for subscription/managementGroup by adding similar logic:

bicep/src/Bicep.Core/Emit/ScopeHelper.cs

Lines 151 to 170 in 6e85607

	if (StringComparer.OrdinalIgnoreCase.Equals(resourceType.TypeReference.FullyQualifiedType, AzResourceTypeProvider.ResourceTypeResourceGroup))
	{
	// special-case 'Microsoft.Resources/resourceGroups' in order to allow it to create a resourceGroup-scope resource
	var rgScopeProperty = targetResourceSymbol.SafeGetBodyProperty(LanguageConstants.ResourceScopePropertyName);
	var rgNameProperty = targetResourceSymbol.SafeGetBodyProperty(LanguageConstants.ResourceNamePropertyName);
	// ignore diagnostics - these will be collected separately in the pass over resources
	var hasErrors = false;
	var rgScopeData = ScopeHelper.ValidateScope(semanticModel, (_, _, _) => { hasErrors = true; }, resourceType.ValidParentScopes, targetResourceSymbol.DeclaringResource.Value, rgScopeProperty);
	if (rgNameProperty is not null && !hasErrors)
	{
	if (!supportedScopes.HasFlag(ResourceScope.ResourceGroup))
	{
	logInvalidScopeFunc(scopeProperty.Value, ResourceScope.ResourceGroup, supportedScopes);
	return null;
	}
	return new ScopeData { RequestedScope = ResourceScope.ResourceGroup, SubscriptionIdProperty = rgScopeData?.SubscriptionIdProperty, ResourceGroupProperty = rgNameProperty.Value, IndexExpression = indexExpression };
	}
	}

[slapointe]

I've encountered this problem too. I declare an existing MG as a resource and cannot use it as a managemenGroup scope to other modules and resources.