[API] pull notification subject status: add "merged" (#15344)
[API] pull notification subject status: add "merged" (#15344)

Current subject status can be "", "open" and "closed". This add "merged" to it.
vdbt/gitea,cez81/gitea,go-gitea/gitea,vdbt/gitea,go-gitea/gitea,cez81/gitea,go-gitea/gitea,cez81/gitea