Add documentation about concurrent asyncio tasks

Author: febus982

docs/lifecycle.md

@@ -20,14 +20,18 @@ database access is potentially anticipated.
 The repository starts a `Session` for each _operation_, in order to maintain isolation.
 This means you can create a repository object almost whenever you want.
 
-/// details | The only exception is creating repositories in global variables!
+/// details | There two exceptions: creating repositories in global variables or concurrent asyncio tasks
     type: warning
-The repository creates a session object, which is not thread safe, to avoid
+The repository creates and maintain the lifecycle of a session object to avoid
 emitting unnecessary queries to refresh the model state on new session.
 
-Being the session object not thread safe, the repository is not thread safe as well.
+The session is not thread safe, therefore the repository is not thread safe as well.
 
 Check the [Notes on multithreaded applications](/manager/session/#note-on-multithreaded-applications)
+
+The `AsyncSession` [is not safe on concurrent asyncio tasks](https://docs.sqlalchemy.org/en/20/orm/session_basics.html#is-the-session-thread-safe-is-asyncsession-safe-to-share-in-concurrent-tasks),
+therefore the same repository instance can't be used in multiple asyncio tasks like
+when using `asyncio.gather()`
 ///
 
 Even using multiple repository instances will work fine, however as they will have completely
@@ -67,7 +71,7 @@ update_my_model()
 ```
 ///
 
-The recommendation is of course to use the same repository instance where possible,
+The recommendation is of course to use the same repository instance, where possible,
 and structure your code in a way to match the single repository instance approach.
 
 For example a strategy similar to this would be optimal, if possible:
@@ -77,6 +81,10 @@ For example a strategy similar to this would be optimal, if possible:
 * Do the changes you need, as per business logic
 * Save all the changed models as needed
 
+/// tip | Using multiple repository instances is the only way to safely use concurrent asyncio tasks
+
+///
+
 ### Unit of work
 
 The Unit of Work session management follows the **same exact rules as the repository**,