Improve logs for Mattermost Push Proxy

Description

We have the Mattermost Push proxy deployed on Kubernetes to serve the community server.
Checking the pod/logs we cannot see any logs generated by the application.

This ticket is about improving the logging for push proxy and uses the structured logging similar we have for mattermost server.

QA Test Steps

None

Status

Mana

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Assignee

Unassigned

QA Assignee

None

Reporter

Carlos Panato

Epic Link

None

Fix versions

Mattermost Team

Cloud

Sprint

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Labels

None

QA Testing Areas

Notifications - Push

GitHub Issue

None
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