reference global logrus (#274)

* reference logrus' global logger instead of passing and storing a logger reference everywhere

* always directly use global logrus logger instead of referencing an instance

* test suites should also directly use the global logrus logger

* rename gin logging function to clarify that it's middleware

* correct comments which erroneously referenced removed logger parameter

* setting log level for tests now uses logrus' exported type instead of the string value, to guarantee error isn't possible

internal/federation/federatingdb/exists.go

@@ -32,7 +32,7 @@ import (
 //
 // Implementation note: this just straight up isn't implemented, and doesn't *really* need to be either.
 func (f *federatingDB) Exists(c context.Context, id *url.URL) (exists bool, err error) {
-	l := f.log.WithFields(
+	l := logrus.WithFields(
 		logrus.Fields{
 			"func": "Exists",
 			"id":   id,