PostHog Cloud authenticates via CIMD OAuth (public client, PKCE)
through the region-agnostic oauth.posthog.com gateway, with an API-key
fallback. PostHog Self-Hosted is a separate provider using an API key
and an instance URL.
The shared driver discovers the data region by probing us/eu for OAuth
connections, since the gateway does not serve the data API, and pins
pagination to the resolved host.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
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