feat: Redo endpoint logic (#39)

[vrongmeal]

Fixes: #39

[vrongmeal]

I have added an example for getting endpoints from environment (like we would want to).

[shikhar]

As a followup, see the note about not including S2-Basin header when it is part of the URI -- it's not a meaningful cost, it's mainly to have a source of continuous validation that we handle it correctly.

[vrongmeal]

Made the requested changes.

As a followup, see the note about not including S2-Basin header when it is part of the URI -- it's not a meaningful cost, it's mainly to have a source of continuous validation that we handle it correctly.

Can you clarify which note? We don't send the basin header if it's part of the URI, that is handled properly I believe.

Moreover, I was thinking of adding some validation on SDK side to only allow a few valid basin zones after https://github.com/s2-streamstore/s2/pull/395 since setting a basin zone implies we want to send basin name in the URI here.

[shikhar]

Pushed some tweaks! Feel free to merge if LGTY too. Regarding the additional validation, can be a followup?

[vrongmeal]

Regarding the additional validation, can be a followup?

Yup, once the server side changes are pushed.