🤖 Add Feature Flag for Event Attachments in StreamGroupSerializer

[sentry-autofix]

👋 Hi there! This PR was automatically generated by Autofix 🤖

This fix was triggered by Josh Ferge

Fixes SENTRY-3KQ6

This pull request introduces a feature flag for event attachments in the StreamGroupSerializer. It modifies the StreamGroupSerializerSnuba class to check for the 'organizations:event-attachments' feature flag during serialization. If the feature is disabled, a ValidationError is raised when attempting to access event attachments. Additionally, a new test case is added in test_group_stream.py to verify the behavior of the serializer when the feature flag is toggled, ensuring it properly handles both enabled and disabled states.

If you have any questions or feedback for the Sentry team about this fix, please email [email protected] with the Run ID: 2437.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
17330	1	17329	191

View the top 1 failed tests by shortest run time

tests.sentry.api.serializers.test_group_stream.StreamGroupSerializerTestCase::test_event_attachments_feature_flag

Stack Traces | 2.87s run time

#x1B[1m#x1B[.../api/serializers/test_group_stream.py#x1B[0m:98: in test_event_attachments_feature_flag
    serializer.get_attrs(item_list=[group], user=request.user, request=request)
#x1B[1m#x1B[.../serializers/models/group_stream.py#x1B[0m:402: in get_attrs
    item.project.organization,
#x1B[1m#x1B[31mE   UnboundLocalError: cannot access local variable 'item' where it is not associated with a value#x1B[0m

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[getsantry]

This pull request 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 add the label WIP, I will leave it alone unless WIP is removed ... forever!

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