Support logr.Marshaler and fmt.Stringer

[hn8]

No description provided.

[hn8]

@pohly @thockin Just an idea to support logr.Marshaler for zerologr. Users could use WithMarshaler() to optionally enable this feature with minor extra overhead. Since logr passes in interface{} variadic spread, hopefully safe to mutate interface slice shallowly in MapFilter function.

[thockin]

I'm not keen on this particular pattern - it's going to require multiple calls to set up.

What about an options struct with a field to "support standard transformations"?

Or what about not making it an option? How much does this hurt critical benchmarks? I considered it important enough to default to "on" for funcr.

[hn8]

@thockin Changed to enable standard transformations by default. Still allow global customization since users may prefer json.Marshaler (current behavior) to fmt.Stringer (new behavior) or need key renaming and value reshaping.