feat: implement a client for Thoth, the IP reputation database for Anubis (#637)

* feat(internal): add Thoth client and simple ASN checker

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(thoth): cached ip to asn checker

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: go mod tidy

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(thoth): minor testing fixups, ensure ASNChecker is Checker

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(thoth): make ASNChecker instances

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(thoth): add GeoIP checker

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(thoth): store a thoth client in a context

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: refactor Checker type to its own package

Signed-off-by: Xe Iaso <me@xeiaso.net>

* test(thoth): add thoth mocking package, ignore context deadline exceeded errors

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(thoth): pre-cache private ranges

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(lib/policy/config): enable thoth ASNs and GeoIP checker parsing

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(thoth): refactor to move checker creation to the checker files

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(policy): enable thoth checks

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(thothmock): test helper function for loading a mock thoth instance

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat: wire up Thoth, make thoth checks part of the default config

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(thoth): mend staticcheck errors

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs(admin): add Thoth docs

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(policy): update Thoth links in error messages

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs: update CHANGELOG

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(docs/manifest): enable Thoth

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: add THOTH_INSECURE for contacting Thoth over plain TCP in extreme circumstances

Signed-off-by: Xe Iaso <me@xeiaso.net>

* test(thoth): use mock thoth when credentials aren't detected in the environment

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(cmd/anubis): better warnings for half-configured Thoth setups

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs(botpolicies): link to Thoth geoip docs

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>

.github/actions/spelling/excludes.txt

@@ -83,6 +83,7 @@
 ^\Q.github/FUNDING.yml\E$
 ^\Q.github/workflows/spelling.yml\E$
 ^data/crawlers/
+^docs/manifest/.*$
 ^docs/static/\.nojekyll$
 ignore$
-robots.txt
+robots.txt