Add subcription feature

services/tenant/app/models/tenants.py

@@ -147,14 +147,22 @@ class TenantMember(Base):
 
 # Additional models for subscriptions, plans, etc.
 class Subscription(Base):
-    """Subscription model for tenant billing"""
+    """Subscription model for tenant billing with tenant linking support"""
     __tablename__ = "subscriptions"
     
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
-    tenant_id = Column(UUID(as_uuid=True), ForeignKey("tenants.id", ondelete="CASCADE"), nullable=False)
+    tenant_id = Column(UUID(as_uuid=True), ForeignKey("tenants.id", ondelete="CASCADE"), nullable=True)
+    
+    # User reference for tenant-independent subscriptions
+    user_id = Column(UUID(as_uuid=True), nullable=True, index=True)
+    
+    # Tenant linking status
+    is_tenant_linked = Column(Boolean, default=False, nullable=False)
+    tenant_linking_status = Column(String(50), nullable=True)  # pending, completed, failed
+    linked_at = Column(DateTime(timezone=True), nullable=True)
     
     plan = Column(String(50), default="starter")  # starter, professional, enterprise
-    status = Column(String(50), default="active")  # active, pending_cancellation, inactive, suspended
+    status = Column(String(50), default="active")  # active, pending_cancellation, inactive, suspended, pending_tenant_linking
 
     # Billing
     monthly_price = Column(Float, default=0.0)
@@ -182,4 +190,14 @@ class Subscription(Base):
     tenant = relationship("Tenant")
     
     def __repr__(self):
-        return f"<Subscription(tenant_id={self.tenant_id}, plan={self.plan}, status={self.status})>"
+        return f"<Subscription(id={self.id}, tenant_id={self.tenant_id}, user_id={self.user_id}, plan={self.plan}, status={self.status})>"
+    
+    def is_pending_tenant_linking(self) -> bool:
+        """Check if subscription is waiting to be linked to a tenant"""
+        return self.tenant_linking_status == "pending" and not self.is_tenant_linked
+    
+    def can_be_linked_to_tenant(self, user_id: str) -> bool:
+        """Check if subscription can be linked to a tenant by the given user"""
+        return (self.is_pending_tenant_linking() and 
+                str(self.user_id) == user_id and
+                self.tenant_id is None)