add API for tenant function (#2866)

### What problem does this PR solve?

feat: API access key management
https://github.com/infiniflow/ragflow/issues/2846
feat: Render markdown file with remark-loader
https://github.com/infiniflow/ragflow/issues/2846

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/db/__init__.py

@@ -27,6 +27,7 @@ class UserTenantRole(StrEnum):
     OWNER = 'owner'
     ADMIN = 'admin'
     NORMAL = 'normal'
+    INVITE = 'invite'
 
 
 class TenantPermission(StrEnum):