Resolves the response media type for a request by negotiating the Accept
header against the producers available in the request's context (relation,
RPC, or root), mirroring PostgREST's content negotiation.
Returns {:ok, %Bier.MediaType{}} or {:error, {:not_acceptable, accept}}
where accept is the original Accept header (used to build the PGRST107
error message).
Summary
Functions
The raw Accept header (or nil).
Negotiate for a request given the list of available producer symbols.
available is an ordered list; its head is the default for */*.