Refactor and improve code consistency across multiple files

- Enhanced SQL queries in `session.go` and `share.go` for clarity and consistency.
- Updated comments for better understanding and maintenance.
- Ensured consistent error handling and return statements across various methods.

backend/internal/models/document.go

@@ -14,28 +14,26 @@ const (
 )
 
 type Document struct {
-    ID        uuid.UUID     `json:"id"`
-    Name      string        `json:"name"`
-    Type      DocumentType  `json:"type"`
-    YjsState  []byte        `json:"-"`
-    OwnerID   *uuid.UUID    `json:"owner_id"` // NEW
-    Is_Public bool          `json:"is_public"`
-    CreatedAt time.Time     `json:"created_at"`
-    UpdatedAt time.Time     `json:"updated_at"`
+	ID        uuid.UUID    `json:"id"`
+	Name      string       `json:"name"`
+	Type      DocumentType `json:"type"`
+	YjsState  []byte       `json:"-"`
+	OwnerID   *uuid.UUID   `json:"owner_id"` // NEW
+	Is_Public bool         `json:"is_public"`
+	CreatedAt time.Time    `json:"created_at"`
+	UpdatedAt time.Time    `json:"updated_at"`
 }
 
-
 type CreateDocumentRequest struct {
-  	Name string       `json:"name" binding:"required"`
-  	Type DocumentType `json:"type" binding:"required"`
-  }
+	Name string       `json:"name" binding:"required"`
+	Type DocumentType `json:"type" binding:"required"`
+}
 
-  type UpdateStateRequest struct {
-  	State []byte `json:"state" binding:"required"`
-  }
-
-  type DocumentListResponse struct {
-  	Documents []Document `json:"documents"`
-  	Total     int        `json:"total"`
-  }
+type UpdateStateRequest struct {
+	State []byte `json:"state" binding:"required"`
+}
 
+type DocumentListResponse struct {
+	Documents []Document `json:"documents"`
+	Total     int        `json:"total"`
+}