[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/api/fileserver/fileserver.go

@@ -0,0 +1,54 @@
+/*
+   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 fileserver
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/processing"
+)
+
+const (
+	// AccountIDKey is the url key for account id (an account ulid)
+	AccountIDKey = "account_id"
+	// MediaTypeKey is the url key for media type (usually something like attachment or header etc)
+	MediaTypeKey = "media_type"
+	// MediaSizeKey is the url key for the desired media size--original/small/static
+	MediaSizeKey = "media_size"
+	// FileNameKey is the actual filename being sought. Will usually be a UUID then something like .jpeg
+	FileNameKey = "file_name"
+	// FileServePath is the fileserve path minus the 'fileserver' prefix.
+	FileServePath = "/:" + AccountIDKey + "/:" + MediaTypeKey + "/:" + MediaSizeKey + "/:" + FileNameKey
+)
+
+type Module struct {
+	processor processing.Processor
+}
+
+func New(processor processing.Processor) *Module {
+	return &Module{
+		processor: processor,
+	}
+}
+
+func (m *Module) Route(attachHandler func(method string, path string, f ...gin.HandlerFunc) gin.IRoutes) {
+	attachHandler(http.MethodGet, FileServePath, m.ServeFile)
+	attachHandler(http.MethodHead, FileServePath, m.ServeFile)
+}