feat(client): Add support for SSH tunneling (#1298)

* feat(client): Add support for SSH tunneling

* Fix test

config/tunneling/tunneling.go

@@ -0,0 +1,70 @@
+package tunneling
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+
+	"github.com/TwiN/gatus/v5/config/tunneling/sshtunnel"
+)
+
+// Config represents the tunneling configuration
+type Config struct {
+	// Tunnels is a map of SSH tunnel configurations in which the key is the name of the tunnel
+	Tunnels map[string]*sshtunnel.Config `yaml:",inline"`
+
+	mu          sync.RWMutex                  `yaml:"-"`
+	connections map[string]*sshtunnel.SSHTunnel `yaml:"-"`
+}
+
+// ValidateAndSetDefaults validates the tunneling configuration and sets defaults
+func (tc *Config) ValidateAndSetDefaults() error {
+	if tc.connections == nil {
+		tc.connections = make(map[string]*sshtunnel.SSHTunnel)
+	}
+	for name, config := range tc.Tunnels {
+		if err := config.ValidateAndSetDefaults(); err != nil {
+			return fmt.Errorf("tunnel '%s': %w", name, err)
+		}
+	}
+	return nil
+}
+
+// GetTunnel returns the SSH tunnel for the given name, creating it if necessary
+func (tc *Config) GetTunnel(name string) (*sshtunnel.SSHTunnel, error) {
+	if name == "" {
+		return nil, fmt.Errorf("tunnel name cannot be empty")
+	}
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+	// Check if tunnel already exists
+	if tunnel, exists := tc.connections[name]; exists {
+		return tunnel, nil
+	}
+	// Get config for this tunnel
+	config, exists := tc.Tunnels[name]
+	if !exists {
+		return nil, fmt.Errorf("tunnel '%s' not found in configuration", name)
+	}
+	// Create and store new tunnel
+	tunnel := sshtunnel.New(config)
+	tc.connections[name] = tunnel
+	return tunnel, nil
+}
+
+// Close closes all SSH tunnel connections
+func (tc *Config) Close() error {
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+	var errors []string
+	for name, tunnel := range tc.connections {
+		if err := tunnel.Close(); err != nil {
+			errors = append(errors, fmt.Sprintf("tunnel '%s': %v", name, err))
+		}
+		delete(tc.connections, name)
+	}
+	if len(errors) > 0 {
+		return fmt.Errorf("failed to close tunnels: %s", strings.Join(errors, ", "))
+	}
+	return nil
+}