As per https://github.com/rs/zerolog/issues/9 and to offer a different approach from https://github.com/rs/zerolog/pull/11 and https://github.com/rs/zerolog/pull/35 this PR introduces custom error serialization with sane defaults without breaking the existing APIs.
This is just a first draft and is missing tests. Also, a bit of code duplication which I feel could be reduced but it serves to get the idea across.
It provides global error marshalling by exposing a `var ErrorMarshalFunc func(error) interface{}` in zerolog package that by default is a function that returns the passed argument. It should be overriden if you require custom error marshalling.
Then in every function that accept error or array of errors `ErrorMarshalFunc` is called on the error and then the result of it is processed like this:
- if it implements `LogObjectMarshaler`, serialize it as an object
- if it is a string serialize as a string
- if it is an error, serialize as a string with the result of `Error()`
- else serialize it as an interface
The side effect of this change is that the encoders don't need the `AppendError/s` methods anymore, as the errors are serialized directly to other types.
Low-level optimizations to help the compiler generate better code
when logging is disabled. Measured improvement is ~30% on amd64
(from 21 ns/op to 16 ns/op).
