CHW-4618 RepoTeamMappingConflict

repo→team mapping with this pattern already exists in the organisation

Default message: repo→team mapping with this pattern already exists in the organisation
HTTP status: 409 (client)

Problem. Creating a repo→team mapping returned 409. Cause. A mapping with the same pattern already exists in this org. Fix. Update the existing mapping instead of creating a new one, or pick a different pattern. HTTP 409.