CHW-4616 RepoTeamMappingInvalid

repo→team mapping payload failed validation; both repoPattern and team are required

Default message: repo→team mapping payload failed validation; both repoPattern and team are required
HTTP status: 400 (client)

Problem. A repo→team mapping create or update returned 400. Cause. Validation failed — typically an empty pattern or empty team. Fix. Supply a non-empty pattern (regex or glob, depending on the route) and a non-empty team identifier. HTTP 400.