[chore] Make paging logic more generic (#901)

* make paging logic more generic
not just for timelines!

* linty linterson

internal/api/model/paging.go

@@ -0,0 +1,28 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package model
+
+// PageableResponse wraps a slice of items, ready to be serialized, along with the Link
+// header for the previous and next queries / pages, to be returned to the client.
+type PageableResponse struct {
+	Items      []interface{}
+	LinkHeader string
+	NextLink   string
+	PrevLink   string
+}