[MM-13840] Change eMail as a post-verification action (#10253)

* Change eMail as a post-verification action

* Fix broken test

* comment for special behavior, tests

* govet

* Check for already existent eMails when require email verification is turned on before accepting update

manualtesting/manual_testing.go

@@ -102,7 +102,7 @@ func manualTest(c *web.Context, w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
-		<-c.App.Srv.Store.User().VerifyEmail(user.Id)
+		<-c.App.Srv.Store.User().VerifyEmail(user.Id, user.Email)
 		<-c.App.Srv.Store.Team().SaveMember(&model.TeamMember{TeamId: teamID, UserId: user.Id}, *c.App.Config().TeamSettings.MaxUsersPerTeam)
 
 		userID = user.Id