Add Inquiry Management Functionality and Update API Documentation

- Introduced a new inquiry management feature, including CRUD operations for inquiries in both admin and public API endpoints.
- Implemented inquiry entity, service, repository, and handler layers following the clean architecture principles.
- Added new API routes for searching, retrieving, updating, and deleting inquiries, enhancing the overall functionality of the system.
- Updated Swagger documentation to include detailed descriptions and examples for the new inquiry endpoints, ensuring clarity for API consumers.
- Enhanced error handling for duplicate inquiries and validation, improving the robustness of the inquiry management process.
- Updated existing routes to integrate inquiry handling, ensuring a seamless user experience across the application.

internal/inquiry/errors.go

@@ -0,0 +1,43 @@
+package inquiry
+
+import "errors"
+
+// Inquiry-specific errors
+var (
+	ErrDuplicateInquiryByEmail = errors.New("duplicate inquiry by email")
+	ErrDuplicateInquiryByPhone = errors.New("duplicate inquiry by phone")
+	ErrInquiryNotFound         = errors.New("inquiry not found")
+	ErrInvalidStatusTransition = errors.New("invalid status transition")
+	ErrInquiryAlreadyProcessed = errors.New("inquiry already processed")
+)
+
+// DuplicateInquiryError represents a duplicate inquiry error with details
+type DuplicateInquiryError struct {
+	Type        string `json:"type"`        // "email" or "phone"
+	ExistingID  string `json:"existing_id"` // ID of existing inquiry
+	Status      string `json:"status"`      // Status of existing inquiry
+	CreatedAt   int64  `json:"created_at"`  // When existing inquiry was created
+	Message     string `json:"message"`     // User-friendly message
+}
+
+func (e *DuplicateInquiryError) Error() string {
+	return e.Message
+}
+
+// NewDuplicateInquiryError creates a new duplicate inquiry error
+func NewDuplicateInquiryError(inquiryType, existingID, status string, createdAt int64) *DuplicateInquiryError {
+	var message string
+	if inquiryType == "email" {
+		message = "You already have a pending inquiry with this email address. Please wait for it to be processed before submitting a new one."
+	} else {
+		message = "A pending inquiry already exists with this phone number. Please wait for it to be processed before submitting a new one."
+	}
+
+	return &DuplicateInquiryError{
+		Type:       inquiryType,
+		ExistingID: existingID,
+		Status:     status,
+		CreatedAt:  createdAt,
+		Message:    message,
+	}
+}