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/processing/fromfederator.go

@@ -35,7 +35,7 @@ import (
 // and directs the message into the appropriate side effect handler function, or simply does nothing if there's
 // no handler function defined for the combination of Activity and Object.
 func (p *processor) ProcessFromFederator(ctx context.Context, federatorMsg messages.FromFederator) error {
-	l := p.log.WithFields(logrus.Fields{
+	l := logrus.WithFields(logrus.Fields{
 		"func":           "processFromFederator",
 		"APActivityType": federatorMsg.APActivityType,
 		"APObjectType":   federatorMsg.APObjectType,