zulip: sync stream membership

[davidtwco]

See rust-lang/team#1604 for the other half of this.

t-compiler want to use our private Zulip stream for some communications but we've held off on doing this as the membership of that stream is manually managed, that is inconvenient and we sometimes forget. In testing this patch, I found the stream membership was still out-of-sync!

I've ran this in dry run mode and it works, so the only thing that needs testing is the API requests for adding and removing subscribers, and that the token that runs this will have permissions to make the change.

I've deliberately avoided adding any automation for the creation of streams, it assumes they exist as this is all that the compiler team needs. There's a reasonable amount of duplication with the types and functions for Zulip user groups, but given that it's largely modelling the upstream API, and we'll likely extend these types to manage more about streams, I think that's okay. Everything I've added should be reusable and compatible with managing streams fully, but I'll leave that for other patches like rust-lang/team#1244.

[MarcoIeni]

Hi, thanks for this PR! Can you fix the clippy error in CI?

[davidtwco]

Hi, thanks for this PR! Can you fix the clippy error in CI?

I think the clippy errors are just because the rust-lang/team changes that it depends on aren't merged.

[MarcoIeni]

Looks good apart from a few minor comments 👍

[MarcoIeni]

I've deliberately avoided adding any automation for the creation of streams, it assumes they exist as this is all that the compiler team needs.

Sure, no worries, I created #93 👍

[pietroalbini]

Thanks for making a PR for this! I wanted this for so long ❤️

Given that running this on a public stream would forcibly remove every non-team-member, I suggest we either error if we try to sync a public stream (as a safeguard), or in public streams we only add, not remove, people.

and that the token that runs this will have permissions to make the change.

This is going to be tricky, since that token cannot exist. Zulip allows only the subscribers of a stream to add or remove other subscribers, nobody else can do it (not even the owners of the Zulip instance). This means we'll need to first add a bot account (rust-lang-owner) to every private stream, and then create a token for that account.

[MarcoIeni]

This means we'll need to first add a bot account (rust-lang-owner) to every private stream, and then create a token for that account.

Does this mean that if an infra admin logs into zulip as rust-lang-owner they can read any private stream without being noticed?
Also, I'm not sure if this is already the case.

[pietroalbini]

Does this mean that if an infra admin logs into zulip as rust-lang-owner they can read any private stream without being noticed?

Yes, this would be based on trust that privileges are not abused.

Also, I'm not sure if this is already the case.

It's not.

[davidtwco]

or in public streams we only add, not remove, people

Added support for this

[MarcoIeni]

Yes, this would be based on trust that privileges are not abused.

Ok, let's make sure everybody is aware of this 👍

E.g. we could add a comment to the toml schema.

[MarcoIeni]

This means we'll need to first add a bot account (rust-lang-owner) to every private stream, and then create a token for that account.

This sounds like a separate PR that we need to merge before this. I guess we don't want to add rust-lang-owner in the toml files. Instead, we want to automatically add this account from the sync team code, listing all private streams and editing them automatically, right?

Another approach would be to only add the account to private streams that are present in the team toml files. I think it might be better for a privacy point of view.

What's the zulip id of the rust-lang-owner user? Can you link to the account? I couldn't find it. Maybe it doesn't exist yet 🤔