To achieve this signatures are now generated by a custom
Tesla Middleware placed after the FollowRedirects Middleware.
Any requests which should be signed needs
to pass the signing key via opts.
This also unifies the associated header logic between fetching and
publishing, notably resolving a divergence wrt the "host" header.
Relevant spec demands the host header shall include a port
identification if not using the protocols standard port.
Fixes: https://akkoma.dev/AkkomaGang/akkoma/issues/731
This matches behaviour prioir to the SigningKey migration
and the expected semantics of the http_signatures lib.
Additionally add a min interval paramter, to avoid
refetch floods on bugs causing incompatible signatures
(like e.g. currently with Bridgy)
Previously there were mainly two attack vectors:
- for raw keys the owner <-> key mapping wasn't verified at all
- keys were retrieved with refetching allowed
and only the top-level ID was sanitised while
usually keys are but a subobject
This reintroduces public key checks in the user actor,
previously removed in 9728e2f8f7
but now adapted to account for the new mapping mechanism.
