refactor(api): restructured API for type safety, maintainability and docs generation

- These changes makes the API incombatible with previous versions
- Added new types for error handling, success responses, and health checks.
- Updated health check logic to utilize the new types for better clarity and structure.
- Refactored existing handlers to improve response consistency and error handling.
- Updated Makefile to include a new target for generating API types from Swagger.
- Updated "new agent" API to respond an encrypted cert pair

internal/types/loadbalancer.go

@@ -0,0 +1,54 @@
+package types
+
+import (
+	"net/http"
+
+	nettypes "github.com/yusing/go-proxy/internal/net/types"
+	"github.com/yusing/go-proxy/internal/utils/strutils"
+)
+
+type (
+	LoadBalancerConfig struct {
+		Link    string           `json:"link"`
+		Mode    LoadBalancerMode `json:"mode"`
+		Weight  int              `json:"weight"`
+		Options map[string]any   `json:"options,omitempty"`
+	} // @name LoadBalancerConfig
+	LoadBalancerMode   string // @name LoadBalancerMode
+	LoadBalancerServer interface {
+		http.Handler
+		HealthMonitor
+		Name() string
+		Key() string
+		URL() *nettypes.URL
+		Weight() int
+		SetWeight(weight int)
+		TryWake() error
+	}
+	LoadBalancerServers []LoadBalancerServer
+)
+
+const (
+	LoadbalanceModeUnset      LoadBalancerMode = ""
+	LoadbalanceModeRoundRobin LoadBalancerMode = "roundrobin"
+	LoadbalanceModeLeastConn  LoadBalancerMode = "leastconn"
+	LoadbalanceModeIPHash     LoadBalancerMode = "iphash"
+)
+
+func (mode *LoadBalancerMode) ValidateUpdate() bool {
+	switch strutils.ToLowerNoSnake(string(*mode)) {
+	case "":
+		return true
+	case string(LoadbalanceModeRoundRobin):
+		*mode = LoadbalanceModeRoundRobin
+		return true
+	case string(LoadbalanceModeLeastConn):
+		*mode = LoadbalanceModeLeastConn
+		return true
+	case string(LoadbalanceModeIPHash):
+		*mode = LoadbalanceModeIPHash
+		return true
+	}
+	*mode = LoadbalanceModeRoundRobin
+	return false
+}