[chore] The Big Middleware and API Refactor (tm) (#1250)

* interim commit: start refactoring middlewares into package under router

* another interim commit, this is becoming a big job

* another fucking massive interim commit

* refactor bookmarks to new style

* ambassador, wiz zeze commits you are spoiling uz

* she compiles, we're getting there

* we're just normal men; we're just innocent men

* apiutil

* whoopsie

* i'm glad noone reads commit msgs haha :blob_sweat:

* use that weirdo go-bytesize library for maxMultipartMemory

* fix media module paths

internal/middleware/extraheaders.go

@@ -0,0 +1,37 @@
+/*
+   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 middleware
+
+import "github.com/gin-gonic/gin"
+
+// ExtraHeaders returns a new gin middleware which adds various extra headers to the response.
+func ExtraHeaders() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Inform all callers which server implementation this is.
+		c.Header("Server", "gotosocial")
+		// Prevent google chrome cohort tracking. Originally this was referred
+		// to as FlocBlock. Floc was replaced by Topics in 2022 and the spec says
+		// that interest-cohort will also block Topics (as of 2022-Nov).
+		//
+		// See: https://smartframe.io/blog/google-topics-api-everything-you-need-to-know
+		//
+		// See: https://github.com/patcg-individual-drafts/topics
+		c.Header("Permissions-Policy", "browsing-topics=()")
+	}
+}