Slack Install Url

Return a Slack authorize URL with an HMAC-signed, short-TTL state.

The signed state carries the authenticated principal's tenant_id so the OAuth callback can attach the Slack workspace to the correct tenant. Callers cannot influence which tenant the state targets: only members holding integrations:edit on a tenant can initiate the install for that tenant, and the tenant identity comes exclusively from the bearer token.

return_path is the dashboard page the user clicked Connect from; the callback sends the browser back there with the outcome flag. The body is optional so a bodyless POST still mints a URL.

Two different limits apply, deliberately. The schema's 2048 max_length is a payload guard only: it 422s a body no real dashboard route could produce. The limit that decides where the user lands is the much shorter core.redirects.MAX_RETURN_PATH_LENGTH, applied during sanitization. A path that is off-origin or longer than that is silently dropped and the callback falls back to its default landing page, never a 422, because a bad return page must not be the thing that blocks someone from connecting Slack.