chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/server/interfaces.go

@@ -0,0 +1,30 @@
+package server
+
+import (
+	"context"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings"
+	"github.com/qdm12/gluetun/internal/models"
+	publicipmodels "github.com/qdm12/gluetun/internal/publicip/models"
+)
+
+type VPNLooper interface {
+	GetStatus() (status models.LoopStatus)
+	ApplyStatus(ctx context.Context, status models.LoopStatus) (
+		outcome string, err error)
+	GetSettings() (settings settings.VPN)
+}
+
+type DNSLoop interface {
+	ApplyStatus(ctx context.Context, status models.LoopStatus) (
+		outcome string, err error)
+	GetStatus() (status models.LoopStatus)
+}
+
+type PortForwardedGetter interface {
+	GetPortForwarded() (portForwarded uint16)
+}
+
+type PublicIPLoop interface {
+	GetData() (data publicipmodels.IPInfoData)
+}