feat: Implement Steam login initialization logic

- Added SteamLoginInitLogic to handle the initiation of Steam login.
- Created service context for managing configuration and Redis connection.
- Defined types for Steam login requests and callbacks.
- Implemented utility functions for building OpenID query strings and validating responses from Steam.
- Updated go.mod and go.sum to include necessary dependencies.
- Modified GenApi.ps1 script to generate code in the correct directory.

app/internal/logic/steamlogininitlogic.go

@@ -0,0 +1,66 @@
+package logic
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"git.cialloo.com/CiallooWeb/Authenticator/app/internal/svc"
+	"git.cialloo.com/CiallooWeb/Authenticator/app/internal/types"
+	"git.cialloo.com/CiallooWeb/Authenticator/app/internal/utils/steamauth"
+
+	"github.com/google/uuid"
+	"github.com/zeromicro/go-zero/core/logx"
+)
+
+type SteamLoginInitLogic struct {
+	logx.Logger
+	ctx    context.Context
+	svcCtx *svc.ServiceContext
+}
+
+const (
+	// Redis key prefix for storing nonces
+	nonceKeyPrefix = "steam:nonce:"
+	// Nonce expiration time (5 minutes)
+	nonceExpiration = 5 * time.Minute
+)
+
+// Initiate Steam login
+func NewSteamLoginInitLogic(ctx context.Context, svcCtx *svc.ServiceContext) *SteamLoginInitLogic {
+	return &SteamLoginInitLogic{
+		Logger: logx.WithContext(ctx),
+		ctx:    ctx,
+		svcCtx: svcCtx,
+	}
+}
+
+func (l *SteamLoginInitLogic) SteamLoginInit(req *types.SteamLoginInitReq, w http.ResponseWriter, r *http.Request) error {
+	// Generate a unique nonce (UUID) for this login attempt
+	nonce := uuid.New().String()
+
+	// Store the nonce in Redis with expiration
+	nonceKey := nonceKeyPrefix + nonce
+	err := l.svcCtx.Redis.Setex(nonceKey, "1", int(nonceExpiration.Seconds()))
+	if err != nil {
+		l.Logger.Errorf("Failed to store nonce in Redis: %v", err)
+		return fmt.Errorf("failed to initialize login session")
+	}
+
+	// Get the callback URL from config
+	callbackURL := l.svcCtx.Config.Steam.CallbackURL
+
+	// Append nonce to callback URL for validation later
+	callbackURLWithNonce := fmt.Sprintf("%s?nonce=%s", callbackURL, nonce)
+
+	// Build the Steam OpenID redirect URL
+	redirectURL := steamauth.GetRedirectURL(callbackURLWithNonce)
+
+	l.Logger.Infof("Initiating Steam login with nonce: %s, callback URL: %s", nonce, callbackURL)
+
+	// Redirect user directly to Steam
+	http.Redirect(w, r, redirectURL, http.StatusFound)
+
+	return nil
+}