Make `OutputTemplateRenderer` public for custom formatters

[na-pel]

Ask: expose the sink’s internal OutputTemplateRenderer (or an equivalent helper) so developers can reuse its theme + template logic instead of re‑implementing it.

Why

• Console sink already handles colour, token expansion and alignment.
• To add small post‑processing (wrap long lines, indent continuation lines, highlight certain keywords, mask secrets, etc.) we must currently fork the whole sink because the renderer is internal.

Proposed change

-internal class OutputTemplateRenderer : ITextFormatter
+public sealed class OutputTemplateRenderer : ITextFormatter

No behaviour change - just surface the type for reuse.

Minimal usage

sealed class CustomConsoleFormatter : ITextFormatter
{
    // Use OutputTemplateRenderer as the backbone – keeps theme + template intact
    private readonly ITextFormatter inner = new OutputTemplateRenderer(
        theme: Console.IsOutputRedirected || Console.IsErrorRedirected
            ? ConsoleTheme.None
            : SystemConsoleTheme.Literate,
        outputTemplate: "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}");

    public void Format(LogEvent logEvent, TextWriter output)
    {
        using var sw = new StringWriter();
        inner.Format(logEvent, sw);
        var sb = sw.GetStringBuilder();

        // Apply any custom tweaks – wrap, indent, highlight, etc.
        sb.Replace("foo", "bar");
        output.Write(sb);
    }
}

Impact

• Minor SemVer bump; default output untouched.
• Enables community extensions without duplicating sink code.

Related: Issue #68.

Thanks! 🙏

[nblumhardt]

Hi! Check out ExpressionTemplate, in https://github.com/serilog/serilog-expressions. Its designed to fill this role, and has extension points that make working with its internals much easier than would be with OutputTemplate. HTH!

[na-pel]

Thanks for pointing me to Serilog.Expressions - it does give me the hook points I was after (word‑wrap + indent while preserving theme). I’ll experiment with it and close the issue if it meets my needs.