[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/util/signaturectx.go

@@ -0,0 +1,41 @@
+/*
+   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 util
+
+import (
+	"context"
+
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/ap"
+)
+
+// TransferSignatureContext transfers a signature verifier and signature from a gin context to a go context.
+func TransferSignatureContext(c *gin.Context) context.Context {
+	ctx := c.Request.Context()
+
+	if verifier, signed := c.Get(string(ap.ContextRequestingPublicKeyVerifier)); signed {
+		ctx = context.WithValue(ctx, ap.ContextRequestingPublicKeyVerifier, verifier)
+	}
+
+	if signature, signed := c.Get(string(ap.ContextRequestingPublicKeySignature)); signed {
+		ctx = context.WithValue(ctx, ap.ContextRequestingPublicKeySignature, signature)
+	}
+
+	return ctx
+}