Multi-tenant support in Linear adapter

[SamyPesse]

Summary

The Linear adapter was simply not working in its current state: Not supporting multiple workspaces when using clientId/clientSecret; but more importantly throwing an error when trying to fetch the comments.

This PR makes the Linear adapter fully work, in multi-tenant and single-tenant modes.

• Fix Linear adapter: refreshClientCredentialsToken() omits app:mentionable scope #231: fix passing different scopes in single-tenant mode with clientId/clientSecret
• Fix Linear adapter cannot work for a multi-tenant app #345: fix handling installations in different workspaces when passing clientId/clientSecret (multi-tenant mode)
• Fix actor=app mode where Linear will trigger an agent session (https://linear.app/developers/agent-interaction) instead of a normal comment
• Support streaming, both for comments and agent sessions

Test plan

Tests have been updated; but I also tested a build in my application.

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[dancer]

hi @SamyPesse looking into this & just saw a couple of things & ty for the PR!

getUserNameFromProfileUrl hardcoded to gitbook-x this needs updated or would break for others & startTyping missing return as in linear i believe they mention this somewhere on their docs user has 10 seconds to respond to a created even or the session is marked unresponsive

also only one changeset file is needed major is fine!

[SamyPesse]

getUserNameFromProfileUrl hardcoded to gitbook-x this needs updated or would break for others

Oups, fixed.

startTyping missing return as in linear

fixed.

in linear i believe they mention this somewhere on their docs user has 10 seconds to respond to a created even or the session is marked unresponsive

Yes, I'm wondering if the adapter should not directly post an ephemeral message "Thinking" or if we wait for the first call to startTyping (what my app is doing).