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/route/common.go

@@ -3,20 +3,21 @@ package route
 import (
 	"github.com/yusing/go-proxy/internal/gperr"
 	"github.com/yusing/go-proxy/internal/route/routes"
+	"github.com/yusing/go-proxy/internal/types"
 )
 
-func checkExists(r routes.Route) gperr.Error {
+func checkExists(r types.Route) gperr.Error {
 	if r.UseLoadBalance() { // skip checking for load balanced routes
 		return nil
 	}
 	var (
-		existing routes.Route
+		existing types.Route
 		ok       bool
 	)
 	switch r := r.(type) {
-	case routes.HTTPRoute:
+	case types.HTTPRoute:
 		existing, ok = routes.HTTP.Get(r.Key())
-	case routes.StreamRoute:
+	case types.StreamRoute:
 		existing, ok = routes.Stream.Get(r.Key())
 	}
 	if ok {