添加 OIDC 和 OAuth2 服务器的基础结构，包括配置、数据库模型、服务、处理器和路由。新增登录页面模板，支持用户认证和授权流程。

handlers/auth.go

@@ -0,0 +1,81 @@
+package handlers
+
+import (
+	"net/http"
+
+	"oidc-oauth2-server/services"
+
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-gonic/gin"
+)
+
+type AuthHandler struct {
+	authService *services.AuthService
+}
+
+type LoginData struct {
+	Error        string
+	RedirectURI  string
+	State        string
+	ClientID     string
+	ResponseType string
+	Scope        string
+}
+
+func NewAuthHandler(authService *services.AuthService) *AuthHandler {
+	return &AuthHandler{
+		authService: authService,
+	}
+}
+
+// ShowLogin 显示登录页面
+func (h *AuthHandler) ShowLogin(c *gin.Context) {
+	data := LoginData{
+		RedirectURI:  c.Query("redirect_uri"),
+		State:        c.Query("state"),
+		ClientID:     c.Query("client_id"),
+		ResponseType: c.Query("response_type"),
+		Scope:        c.Query("scope"),
+	}
+	c.HTML(http.StatusOK, "login.html", data)
+}
+
+// HandleLogin 处理登录请求
+func (h *AuthHandler) HandleLogin(c *gin.Context) {
+	username := c.PostForm("username")
+	password := c.PostForm("password")
+
+	user, err := h.authService.Authenticate(username, password)
+	if err != nil {
+		data := LoginData{
+			Error:        "用户名或密码错误",
+			RedirectURI:  c.PostForm("redirect_uri"),
+			State:        c.PostForm("state"),
+			ClientID:     c.PostForm("client_id"),
+			ResponseType: c.PostForm("response_type"),
+			Scope:        c.PostForm("scope"),
+		}
+		c.HTML(http.StatusOK, "login.html", data)
+		return
+	}
+
+	// 设置用户会话
+	session := sessions.Default(c)
+	session.Set("user_id", user.ID)
+	session.Save()
+
+	// 重定向回授权页面
+	redirectURI := c.PostForm("redirect_uri")
+	if redirectURI == "" {
+		redirectURI = "/authorize"
+	}
+
+	query := c.Request.URL.Query()
+	query.Set("client_id", c.PostForm("client_id"))
+	query.Set("response_type", c.PostForm("response_type"))
+	query.Set("scope", c.PostForm("scope"))
+	query.Set("state", c.PostForm("state"))
+	query.Set("redirect_uri", redirectURI)
+
+	c.Redirect(http.StatusFound, "/authorize?"+query.Encode())
+}