persistRelationship

Persists a single projected relationship to the graph.

Re-saves each resolved entity verbatim (exactly as returned by the repository) before merging the edge, so multi-label nodes like (:Person:User) materialise correctly — the RetrievableIdentifier edge endpoint only carries one type string, so the re-save is how the full label set gets written.

The three repository calls (source save, target save, mergeRelationship) are not transactional within this module. If you need all-or-nothing semantics, wrap this call in a @Transactional boundary in your consuming Spring context.