Runtime: Indenting and unindenting JSON should be easier

[terrajobst]

Imagine I need to unindent some raw JSON (for example, for error messages and logging). There is no simple way to do that; instead, I ended up writing the following, which seems a bit clunky:

```C#
public static string ChangeIndentation(string value, bool indented)
{
using (var stream = new MemoryStream())
{
var options = new JsonWriterOptions { Indented = indented };

    using (var writer = new Utf8JsonWriter(stream, options))
    {
        using var document = JsonDocument.Parse(value);
        document.WriteTo(writer);
    }

    stream.Position = 0;

    using (var reader = new StreamReader(stream))
        return reader.ReadToEnd();
}

}

### Proposal

```C#
namespace System.Text.Json
{
    partial class JsonDocument
    {
        public override string ToString() => ToString(indented: true);
        public string ToString(bool indented);
    }
}

Usage

C# public static string ChangeIndentation(string value, bool indented) { using var document = JsonDocument.Parse(value); return document.ToString(indented); }

[Wraith2]

The idea of seeing document.ToString(true) all over the place doesn't thrill me. How about changing the bool param to a JsonWriterOptions, then you'll end up with something like document.ToString(new JsonWriterOptions{ Indented=true }) which is longer but at least tells you what's going on more clearly. It'll also allow any future writer options to be set without adding to the api surface.

[scalablecory]

Not really sure how I feel about it, but it seems like ToString(string format) should be considered to keep consistency with everything else.

[Jozkee]

Have you tried the following?

public static string ChangeIndentation(string value)
{
    JsonNode node = JsonNode.Parse(value);
    return node.ToJsonString();
}

However I assume using the one you propose with JsonDocument would perform better since its read-only.