Auto enable Sessions for non-WSGI frameworks

[rhcarvalho]

In #994 the SDK was changed such that the WSGI integration and all frameworks that inherit from it have "request-mode" sessions on by default.

However, despite the default auto_session_tracking=True init option, session tracking is not enabled for anything outside of the WSGI realm.

Missing:

• Automatic "application-mode" session for non-Web-servers applications
• Automatic session for non-WSGI integrations (e.g., Django and ASGI)

These are also missing but probably should actually disable sessions altogether (and have accompanying documentation):

• Queue consumers (e.g., Celery and RQ) ⇒ it is unclear doing 1 session per queue item is justified, there is no industry precedence on this to set user expectations

• Serverless (e.g., AWS Lambda and Google Cloud Functions) ⇒ considering that the current implementation requires a separate request to send a session update, this would require a minimum of 2 requests per cloud function invocation (1 for transaction and 1 for session) which would be highly inefficient.

• We need to document what auto_session_tracking enables, clarifying what the behavior is.

[github-actions]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you label it Status: Backlog or Status: In Progress, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[antonpirker]

We started a wider discussion about this inside Sentry. For now this is closed here, because it also involves other SDKs