chore(all): return concrete types, accept interfaces

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

internal/dns/interfaces.go

@@ -0,0 +1,29 @@
+package dns
+
+import (
+	"context"
+
+	"github.com/qdm12/dns/pkg/unbound"
+	"github.com/qdm12/gluetun/internal/configuration/settings"
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+type Configurator interface {
+	SetupFiles(ctx context.Context) error
+	MakeUnboundConf(settings unbound.Settings) (err error)
+	Start(ctx context.Context, verbosityDetailsLevel uint8) (
+		stdoutLines, stderrLines chan string, waitError chan error, err error)
+	Version(ctx context.Context) (version string, err error)
+}
+
+type statusManager interface {
+	GetStatus() (status models.LoopStatus)
+	SetStatus(status models.LoopStatus)
+	ApplyStatus(ctx context.Context, status models.LoopStatus) (
+		outcome string, err error)
+}
+
+type stateManager interface {
+	GetSettings() (settings settings.DNS)
+	SetSettings(ctx context.Context, settings settings.DNS) (outcome string)
+}