feat: Enhance real-time collaboration features with user awareness and document sharing

- Added user information (UserID, UserName, UserAvatar) to Client struct for presence tracking.
- Implemented failure handling in the broadcastMessage function to manage send failures and disconnect clients if necessary.
- Introduced document ownership and sharing capabilities:
  - Added OwnerID and Is_Public fields to Document model.
  - Created DocumentShare model for managing document sharing with permissions.
  - Implemented functions for creating, listing, and managing document shares in the Postgres store.
- Added user management functionality:
  - Created User model and associated functions for user management in the Postgres store.
  - Implemented session management with token hashing for security.
- Updated database schema with migrations for users, sessions, and document shares.
- Enhanced frontend Yjs integration with awareness event logging for user connections and disconnections.

backend/internal/models/document.go

@@ -14,14 +14,17 @@ const (
 )
 
 type Document struct {
-		ID        uuid.UUID    `json:"id"`
-  	Name      string       `json:"name"`
-  	Type      DocumentType `json:"type"`
-  	YjsState  []byte       `json:"-"` // Don't expose binary data in JSON
-  	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"`

backend/internal/models/share.go

@@ -0,0 +1,30 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type DocumentShare struct {
+    ID         uuid.UUID  `json:"id"`
+    DocumentID uuid.UUID  `json:"document_id"`
+    UserID     uuid.UUID  `json:"user_id"`
+    Permission string     `json:"permission"` // "view" or "edit"
+    CreatedAt  time.Time  `json:"created_at"`
+    CreatedBy  *uuid.UUID `json:"created_by"`
+}
+
+type CreateShareRequest struct {
+    UserEmail  string `json:"user_email" binding:"required"`
+    Permission string `json:"permission" binding:"required,oneof=view edit"`
+}
+
+type ShareListResponse struct {
+    Shares []DocumentShareWithUser `json:"shares"`
+}
+
+type DocumentShareWithUser struct {
+    DocumentShare
+    User User `json:"user"`
+}

backend/internal/models/user.go

@@ -0,0 +1,48 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type User struct {
+    ID             uuid.UUID  `json:"id"`
+    Email          string     `json:"email"`
+    Name           string     `json:"name"`
+    AvatarURL      *string    `json:"avatar_url"`
+    Provider       string     `json:"provider"`
+    ProviderUserID string     `json:"-"` // Don't expose
+    CreatedAt      time.Time  `json:"created_at"`
+    UpdatedAt      time.Time  `json:"updated_at"`
+    LastLoginAt    *time.Time `json:"last_login_at"`
+}
+
+type Session struct {
+    ID        uuid.UUID `json:"id"`
+    UserID    uuid.UUID `json:"user_id"`
+    TokenHash string    `json:"-"` // SHA-256 hash of JWT
+    ExpiresAt time.Time `json:"expires_at"`
+    CreatedAt time.Time `json:"created_at"`
+    UserAgent *string   `json:"user_agent"`
+    IPAddress *string   `json:"ip_address"`
+}
+
+type OAuthToken struct {
+    ID           uuid.UUID  `json:"id"`
+    UserID       uuid.UUID  `json:"user_id"`
+    Provider     string     `json:"provider"`
+    AccessToken  string     `json:"-"` // Don't expose
+    RefreshToken *string    `json:"-"`
+    TokenType    string     `json:"token_type"`
+    ExpiresAt    time.Time  `json:"expires_at"`
+    Scope        *string    `json:"scope"`
+    CreatedAt    time.Time  `json:"created_at"`
+    UpdatedAt    time.Time  `json:"updated_at"`
+}
+
+// Response for /auth/me endpoint
+type UserResponse struct {
+    User  *User `json:"user"`
+    Token string `json:"token,omitempty"`
+}