Database updates (#144)

* start moving some database stuff around

* continue moving db stuff around

* more fiddling

* more updates

* and some more

* and yet more

* i broke SOMETHING but what, it's a mystery

* tidy up

* vendor ttlcache

* use ttlcache

* fix up some tests

* rename some stuff

* little reminder

* some more updates

internal/processing/media/update.go

@@ -32,7 +32,7 @@ import (
 func (p *processor) Update(account *gtsmodel.Account, mediaAttachmentID string, form *apimodel.AttachmentUpdateRequest) (*apimodel.Attachment, gtserror.WithCode) {
 	attachment := &gtsmodel.MediaAttachment{}
 	if err := p.db.GetByID(mediaAttachmentID, attachment); err != nil {
-		if _, ok := err.(db.ErrNoEntries); ok {
+		if err == db.ErrNoEntries {
 			// attachment doesn't exist
 			return nil, gtserror.NewErrorNotFound(errors.New("attachment doesn't exist in the db"))
 		}