Re-add ability to set access token independently

[elijahmorg]

What kind of change does this PR introduce?

bug fix / feature. This was already added and then clobbered. See relevant issue.

What is the current behavior?

Please link any relevant issues here.

https://github.com/supabase-community/postgrest-go/issues/32

What is the new behavior?

Feel free to include screenshots if it includes visual changes.

Additional context

Add any other context or screenshots.