Add docs on custom session IDs (#1609)

docs/pages/basics/sessions.md

@@ -92,6 +92,16 @@ interface DatabaseSessionAttributes {
 }
 ```
 
+### Custom session IDs
+
+You use your own session IDs with the `sessionId` option, though we recommend sticking with Lucia's default IDs as they provide a good balance between entropy and compactness. If you're using UUIDs, make sure they're generated using a cryptographically secure random source. Object IDs should not be used as session IDs as they do not provide enough entropy.
+
+```ts
+const session = await lucia.createSession(userId, attributes, {
+ sessionId: generate
+});
+```
+
 ## Validate sessions
 
 Use `Lucia.validateSession()` to validate a session using its ID. This will return an object containing a session and user. Both of these will be `null` if the session is invalid.

docs/pages/reference/main/Lucia/createSession.md

@@ -14,11 +14,16 @@ Method of [`Lucia`](/reference/main/Lucia). Creates a new session.
 //$ UserId=/reference/main/UserId
 function createSession(
  userId: $$UserId,
- attributes: $$DatabaseSessionAttributes
+ attributes: $$DatabaseSessionAttributes,
+ options?: {
+ sessionId?: string;
+ }
 ): Promise<$$Session>;
 ```
 
 ### Parameters
 
 - `userId`
 - `attributes`: Database session attributes
+- `options`:
+ - `sessionId`