Add trailing newline to pretty JSON response

[tyilo]

Motivation

Normally human-readable JSON HTTP response bodies have a trailing newline, so that the body is a valid "text file" and nicer for viewing in the terminal with something like curl.

I think it would make sense that ErasedJson::pretty also had a trailing newline.

Solution

Append a newline to the output of serde_json::to_writer_pretty.