feat(oauth): implement custom OAuth provider management #1106

- Add support for custom OAuth providers, including creation, retrieval, updating, and deletion.
- Introduce new model and controller for managing custom OAuth providers.
- Enhance existing OAuth logic to accommodate custom providers.
- Update API routes for custom OAuth provider management.
- Include i18n support for custom OAuth-related messages.

model/user_oauth_binding.go

@@ -0,0 +1,125 @@
+package model
+
+import (
+	"errors"
+	"time"
+)
+
+// UserOAuthBinding stores the binding relationship between users and custom OAuth providers
+type UserOAuthBinding struct {
+	Id             int       `json:"id" gorm:"primaryKey"`
+	UserId         int       `json:"user_id" gorm:"index;not null"`                                               // User ID
+	ProviderId     int       `json:"provider_id" gorm:"index;not null"`                                           // Custom OAuth provider ID
+	ProviderUserId string    `json:"provider_user_id" gorm:"type:varchar(256);not null"`                          // User ID from OAuth provider
+	CreatedAt      time.Time `json:"created_at"`
+
+	// Composite unique index to prevent duplicate bindings
+	// One OAuth account can only be bound to one user
+}
+
+func (UserOAuthBinding) TableName() string {
+	return "user_oauth_bindings"
+}
+
+// GetUserOAuthBindingsByUserId returns all OAuth bindings for a user
+func GetUserOAuthBindingsByUserId(userId int) ([]*UserOAuthBinding, error) {
+	var bindings []*UserOAuthBinding
+	err := DB.Where("user_id = ?", userId).Find(&bindings).Error
+	return bindings, err
+}
+
+// GetUserOAuthBinding returns a specific binding for a user and provider
+func GetUserOAuthBinding(userId, providerId int) (*UserOAuthBinding, error) {
+	var binding UserOAuthBinding
+	err := DB.Where("user_id = ? AND provider_id = ?", userId, providerId).First(&binding).Error
+	if err != nil {
+		return nil, err
+	}
+	return &binding, nil
+}
+
+// GetUserByOAuthBinding finds a user by provider ID and provider user ID
+func GetUserByOAuthBinding(providerId int, providerUserId string) (*User, error) {
+	var binding UserOAuthBinding
+	err := DB.Where("provider_id = ? AND provider_user_id = ?", providerId, providerUserId).First(&binding).Error
+	if err != nil {
+		return nil, err
+	}
+
+	var user User
+	err = DB.First(&user, binding.UserId).Error
+	if err != nil {
+		return nil, err
+	}
+	return &user, nil
+}
+
+// IsProviderUserIdTaken checks if a provider user ID is already bound to any user
+func IsProviderUserIdTaken(providerId int, providerUserId string) bool {
+	var count int64
+	DB.Model(&UserOAuthBinding{}).Where("provider_id = ? AND provider_user_id = ?", providerId, providerUserId).Count(&count)
+	return count > 0
+}
+
+// CreateUserOAuthBinding creates a new OAuth binding
+func CreateUserOAuthBinding(binding *UserOAuthBinding) error {
+	if binding.UserId == 0 {
+		return errors.New("user ID is required")
+	}
+	if binding.ProviderId == 0 {
+		return errors.New("provider ID is required")
+	}
+	if binding.ProviderUserId == "" {
+		return errors.New("provider user ID is required")
+	}
+
+	// Check if this provider user ID is already taken
+	if IsProviderUserIdTaken(binding.ProviderId, binding.ProviderUserId) {
+		return errors.New("this OAuth account is already bound to another user")
+	}
+
+	binding.CreatedAt = time.Now()
+	return DB.Create(binding).Error
+}
+
+// UpdateUserOAuthBinding updates an existing OAuth binding (e.g., rebind to different OAuth account)
+func UpdateUserOAuthBinding(userId, providerId int, newProviderUserId string) error {
+	// Check if the new provider user ID is already taken by another user
+	var existingBinding UserOAuthBinding
+	err := DB.Where("provider_id = ? AND provider_user_id = ?", providerId, newProviderUserId).First(&existingBinding).Error
+	if err == nil && existingBinding.UserId != userId {
+		return errors.New("this OAuth account is already bound to another user")
+	}
+
+	// Check if user already has a binding for this provider
+	var binding UserOAuthBinding
+	err = DB.Where("user_id = ? AND provider_id = ?", userId, providerId).First(&binding).Error
+	if err != nil {
+		// No existing binding, create new one
+		return CreateUserOAuthBinding(&UserOAuthBinding{
+			UserId:         userId,
+			ProviderId:     providerId,
+			ProviderUserId: newProviderUserId,
+		})
+	}
+
+	// Update existing binding
+	return DB.Model(&binding).Update("provider_user_id", newProviderUserId).Error
+}
+
+// DeleteUserOAuthBinding deletes an OAuth binding
+func DeleteUserOAuthBinding(userId, providerId int) error {
+	return DB.Where("user_id = ? AND provider_id = ?", userId, providerId).Delete(&UserOAuthBinding{}).Error
+}
+
+// DeleteUserOAuthBindingsByUserId deletes all OAuth bindings for a user
+func DeleteUserOAuthBindingsByUserId(userId int) error {
+	return DB.Where("user_id = ?", userId).Delete(&UserOAuthBinding{}).Error
+}
+
+// GetBindingCountByProviderId returns the number of bindings for a provider
+func GetBindingCountByProviderId(providerId int) (int64, error) {
+	var count int64
+	err := DB.Model(&UserOAuthBinding{}).Where("provider_id = ?", providerId).Count(&count).Error
+	return count, err
+}