Add support for JSON based resources

[BernieWhite]

Currently resources such as Baselines, Module Configurations, Rules, and Selectors can be written in YAML.

This is great and offers a good option humans to write these resources.

For some cases it would be helpful to make it easier code to automatically generate these resources. While YAML can be automated, there is much better support for this with JSON, so added JSON support for storing resource would be a good idea.

[ArmaanMcleod]

@BernieWhite Let me know what else we should cover in this issue. Happy to add more JSON support for the other resources like Module Configurations, Rules, and Selectors.

[BernieWhite]

@ArmaanMcleod For this one JSON rule and selector support would be key. This would make it easier to do Azure/PSRule.Rules.Azure#181. Since selectors are a subset of rules enabling both should not be much additional work once rules is done.

Once rules can be written in JSON, we can work to export policies from an Azure subscription to JSON based rules.

---

Currently baselines can be formatted/ exported to JSON however they would not currently be read from JSON by the pipeline.

For example ps1 and YAML rules are pulled into PSRule via:

PSRule/src/PSRule/Host/HostHelper.cs

Lines 35 to 41 in c05a7c7

	internal static Rule[] GetRule(Source[] source, RunspaceContext context, bool includeDependencies)
	{
	var rules = ToRuleV1(GetLanguageBlock(context, source), context);
	var builder = new DependencyGraphBuilder<Rule>(includeDependencies);
	builder.Include(rules, filter: (b) => Match(context, b));
	return builder.GetItems();
	}

.

Other resources via:

PSRule/src/PSRule/Host/HostHelper.cs

Lines 95 to 101 in c05a7c7

	internal static void ImportResource(Source[] source, RunspaceContext context)
	{
	if (source == null || source.Length == 0)
	return;
	Import(ReadYamlObjects(source, context), context);
	}

Sources discovered by:

PSRule/src/PSRule/Pipeline/SourcePipeline.cs

Lines 334 to 338 in c05a7c7

	private static bool ShouldInclude(string path)
	{
	return path.EndsWith(".rule.ps1", System.StringComparison.OrdinalIgnoreCase) ||
	path.EndsWith(".rule.yaml", System.StringComparison.OrdinalIgnoreCase);
	}

[ArmaanMcleod]

Thanks @BernieWhite. I think I'll start by creating a ReadJsonObjects method and implement a JsonConverter for ResourceObject. Will probably have to convert this implementation: https://github.com/microsoft/PSRule/blob/main/src/PSRule/Common/YamlConverters.cs#L473.

What do you think?

[ArmaanMcleod]

To close this out, just need to ensure module configs work with JSON. I havn't tested this, but adding some tests wouldn't hurt.

[BernieWhite]

@ArmaanMcleod Yes, should be fine module configs are the only resource not tested. Let's add tests and close. Thanks.