Admins can now do unlimited page size user search (listAllUsers & listAllOrgs) (#6143)

Non-admins will default to 10 page size

models/user.go

 	if opts.PageSize > 0 {
 		sess = sess.Limit(opts.PageSize, (opts.Page-1)*opts.PageSize)
 	}
+	if opts.PageSize == -1 {
+		opts.PageSize = int(count)
+	}
 
 	users = make([]*User, 0, opts.PageSize)
 	return users, count, sess.OrderBy(opts.OrderBy.String()).Find(&users)

routers/api/v1/user/user.go

 		Type:     models.UserTypeIndividual,
 		PageSize: com.StrTo(ctx.Query("limit")).MustInt(),
 	}
-	if opts.PageSize == 0 {
+	if opts.PageSize <= 0 {
 		opts.PageSize = 10
 	}