Are stream summaries and obsolete messages multiline?
Pros: Compatible with YAML.
Cons: Single-line summary is akin to an RPM summary.
DNF: They can be single-line.
DNF: They can be empty.
DNF: A details specification for obsoletes should have mcurlej.

DECISION
========
A build summary and license are single-line. Other free-form texts are
multi-line.
