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/api/v1/auth/callback.go

@@ -0,0 +1,24 @@
+//nolint:dupword
+package auth
+
+import (
+	"github.com/gin-gonic/gin"
+	"github.com/yusing/go-proxy/internal/auth"
+)
+
+// @x-id				"callback"
+// @Base			/api/v1
+// @Summary		Post Auth Callback
+// @Description	Handles the callback from the provider after successful authentication
+// @Tags			auth
+// @Produce		plain
+// @Param		  body	body	auth.UserPassAuthCallbackRequest	true	"Userpass only"
+// @Success		200	{string}	string	"Userpass: OK"
+// @Success		302	{string}	string	"OIDC: Redirects to home page"
+// @Failure		400	{string}	string	"OIDC: invalid request (missing state cookie or oauth state)"
+// @Failure		400	{string}	string	"Userpass: invalid request / credentials"
+// @Failure		500	{string}	string	"Internal server error"
+// @Router			/auth/callback [post]
+func Callback(c *gin.Context) {
+	auth.GetDefaultAuth().PostAuthCallbackHandler(c.Writer, c.Request)
+}