🐛 Fixed error on saving member with existing label
🐛 Fixed error on saving member with existing label

closes https://github.com/TryGhost/Team/issues/743

Unlike tags, a label has a unique constraint on its `name`. So saving a new label on member with the same name as existing label fails with error due to unique constraint error.

- adds id for new label to match existing label if they are the same name, which avoids creating a new label

e10/Ghost,janvt/Ghost,TryGhost/Ghost,e10/Ghost,ErisDS/Ghost,TryGhost/Ghost,janvt/Ghost,TryGhost/Ghost,ErisDS/Ghost,ErisDS/Ghost