Coordinator guide improvements

[zwilling]

Prerequisites

Please answer the following question for yourself before submitting a feature request.

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Motivation

Following the guide on https://pse-team.notion.site/Coordinator-Guide-9110e0b3c8c1404a9598323731974455 was more difficult that expected. I suggest to add the following troubleshooting points to make is simpler for future users.

Details

1. The cloud logs are a great tool to debug cloud functions. They can be found at https://console.cloud.google.com/logs/
2. When functions, such as registerAuthUser log PERMISSION_DENIED errors, the "App Engine default service account" might require more permissions. (So far the guide only mentions the permissions for the "Default compute service account").
3. checkAndRemoveBlockingContributor sometimes has issues if the database is not indexed. They you can find a link in the logs that leads to the firebase page where the index can be generated.
4. The deployment of verifycontribution might fail because of the CPU and memory quota requested. Halving it might help: https://github.com/privacy-scaling-explorations/p0tion/blob/5b24d8f1eb9682e2a59f2e83945176369cdde12f/packages/backend/src/functions/circuit.ts#L463
5. It might be necessary to add the Cloud Functions Invoker role for allUsers in all http callable functions. Otherwise external users might not be able to register.