[feature] Rework timeline code to make it useful for more than just statuses (#373)

* add preparable and timelineable interfaces

* initialize timeline manager within the processor

* generic renaming

* move status-specific timeline logic into the processor

* refactor timeline to make it useful for more than statuses

internal/timeline/timelineable.go

@@ -0,0 +1,27 @@
+/*
+   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 timeline
+
+// Timelineable represents any item that can be put in a timeline.
+type Timelineable interface {
+	GetID() string
+	GetAccountID() string
+	GetBoostOfID() string
+	GetBoostOfAccountID() string
+}