In version 10.0.0-next.8, we introduced absolute URL support for
server-based HTTP requests, so long as the fully-resolved URL was
provided in the initial config. However, doing so represents a
breaking change for users who already have their own interceptors
to model this functionality, since our logic executes before all
interceptors fire on a request. See original PR #37071.
Therefore, we introduce a flag to make this change consistent with
v9 behavior, allowing users to opt in to this new behavior. This
commit also fixes two issues with the previous implementation:
1. if the server was initiated with a relative URL, the absolute
URL construction would fail because needed components were empty
2. if the user's absolute URL was on a port, the port would not
be included
PR Close#37539