allow push monitors to update prometheus

[wishdev]

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Description

Fixes #2946
The push style of monitor was returning prior to update prometheus which did not allow it to get on the /metrics endpoint.

Type of change

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• Bug fix (non-breaking change which fixes an issue)

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[CommanderStorm]

I am unsure if this return statement is correct in the first place.
This shortcuts a lot of logic, for example
https://github.com/louislam/uptime-kuma/blame/0060e46b91b108c6960858e12da5c2f312437a1b/server/model/monitor.js#L979

CC @kaysond you added this in #1428

I dont quite get why No need to insert successful heartbeat for push type, so end here. Could you explain this?

[kaysond]

I didn't actually add it, just moved it. See: https://github.com/louislam/uptime-kuma/pull/1428/files

But I think it's there because for push type monitors, the API call to the push URL adds the heartbeat to the DB. There's no need for the monitor to add the heartbeat, so everything else is skipped on purpose

[chakflying]

In that case maybe we should update the Prometheus metrics in the push route handler instead.