Improve data warehouse joins when uuid/id column types mismatch

Feature request

Is your feature request related to a problem?

With data warehouse tables the column types can mismatch with those in PostHog tables, resulting in an error beginning with:

Can't infer common type for joined columns

The workaround is to use a SQL expression to coerce the uuid or id into a string type on one or both sides. But it seems that we could detect this situation better and attempt to do it for the user automatically.

Describe the solution you'd like

Better error handling to assist the user, or to do the coercion ourselves for the user.

Describe alternatives you've considered

Additional context

Ticket that encountered this: https://posthoghelp.zendesk.com/agent/tickets/41667 (moved to PostHog: https://us.posthog.com/project/2/support/tickets/44127)

Debug info

- [x] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]

Start by reproducing a data warehouse join between mismatched uuid/id columns and inspect where the “Can't infer common type for joined columns” error is handled. Compare automatic coercion with improved error guidance; done means users can complete the join without the type-mismatch failure or receive actionable guidance, with the linked support tickets providing context.