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

agent/pkg/handler/handler.go

@@ -25,7 +25,9 @@ func NewAgentHandler() http.Handler {
 	mux := ServeMux{http.NewServeMux()}
 
 	mux.HandleFunc(agent.EndpointProxyHTTP+"/{path...}", ProxyHTTP)
-	mux.HandleEndpoint("GET", agent.EndpointVersion, pkg.GetVersionHTTPHandler())
+	mux.HandleEndpoint("GET", agent.EndpointVersion, func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, pkg.GetVersion())
+	})
 	mux.HandleEndpoint("GET", agent.EndpointName, func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprint(w, env.AgentName)
 	})