Alerting on Gauges

[ayirr7]

Add subscriptions setup and infra for gauges so that we can support alerting on them in the Metrics product.

Tasks

Beta Give feedback

1. Add subscriptions consumers and topic locally in Snuba #5745
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2. Add schema for new subscriptions scheduled topic #5771
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3. Fix subscriptions gauges topic configuration in Ops repo #5926
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4. Deploy new subscriptions consumers in SaaS, ST, DE #5927
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[ayirr7]

This is currently blocked by the last task, which involves a SRE dependency.

[ayirr7]

This is complete infrastructure-wise.

The remaining steps include an open investigation on missing organization information in the subscription query's metadata field. This PR #5976 aimed to set up some logs for better visibility into the problem queries.

[enochtangg]

Missing organization information in query metadata only existed for gauges subscriptions that were created before the infrastructure was properly configured. These alerts have been updated/recreated and malformed subscription queries have stopped coming in. Closing this issue.