Maint: cli package interface rework

- return concrete struct type
- split interface is sub-interfaces

internal/cli/cli.go

@@ -1,26 +1,21 @@
 // Package cli defines an interface CLI to run command line operations.
 package cli
 
-import (
-	"context"
+var _ CLIer = (*CLI)(nil)
 
-	"github.com/qdm12/golibs/logging"
-	"github.com/qdm12/golibs/params"
-)
-
-type CLI interface {
-	ClientKey(args []string) error
-	HealthCheck(ctx context.Context, env params.Env, logger logging.Logger) error
-	OpenvpnConfig(logger logging.Logger) error
-	Update(ctx context.Context, args []string, logger logging.Logger) error
+type CLIer interface {
+	ClientKeyFormatter
+	HealthChecker
+	OpenvpnConfigMaker
+	Updater
 }
 
-type cli struct {
+type CLI struct {
 	repoServersPath string
 }
 
-func New() CLI {
-	return &cli{
+func New() *CLI {
+	return &CLI{
 		repoServersPath: "./internal/constants/servers.json",
 	}
 }