Fix #7198 by allowing records with optional attachments to save

to_s method of HTTP::Response keeps blocking while it receives the whole
content, no matter how it is big. This means it may waste time to receive
unacceptably large files. It may also consume memory and disk in the
process. This solves the inefficency by checking response length while
receiving.

HTTP connections must be explicitly closed in many cases, and letting
perform method close connections makes its callers less redundant and
prevent them from forgetting to close connections.

This will prevent, for example, `rake mastodon:redownload_avatars` from crashing when an instance is no longer responding to connection attempts, instead silently continuing as expected.

* Rescue when there's no extension in the remotable
Sometimes the remotable is pointing to a directory with no file
extension. Maybe it should not be expecting to identify based on
extensions to begin with, but since it's the case, it should be ready
for it.

* Fix codeclimate issue

* Check if filename is nil instead of rescueing exception
Suggestion made in the PR

* Avoid concatenation issue if filename is nil
If filename is nil, extname was undefined

* Invert condition
Address PR comments

* Add ActivityPub inbox

* Handle ActivityPub deletes

* Handle ActivityPub creates

* Handle ActivityPub announces

* Stubs for handling all activities that need to be handled

* Add ActivityPub actor resolving

* Handle conversation URI passing in ActivityPub

* Handle content language in ActivityPub

* Send accept header when fetching actor, handle JSON parse errors

* Test for ActivityPub::FetchRemoteAccountService

* Handle public key and icon/image when embedded/as array/as resolvable URI

* Implement ActivityPub::FetchRemoteStatusService

* Add stubs for more interactions

* Undo activities implemented

* Handle out of order activities

* Hook up ActivityPub to ResolveRemoteAccountService, handle
Update Account activities

* Add fragment IDs to all transient activity serializers

* Add tests and fixes

* Add stubs for missing tests

* Add more tests

* Add more tests

* Add Request class with HTTP signature generator

Spec: https://tools.ietf.org/html/draft-cavage-http-signatures-06

* Add HTTP signature verification concern

* Add test for SignatureVerification concern

* Add basic test for Request class

* Make PuSH subscribe/unsubscribe requests use new Request class

Accidentally fix lease_seconds not being set and sent properly, and
change the new minimum subscription duration to 1 day

* Make all PuSH workers use new Request class

* Make Salmon sender use new Request class

* Make FetchLinkService use new Request class

* Make FetchAtomService use the new Request class

* Make Remotable use the new Request class

* Make ResolveRemoteAccountService use the new Request class

* Add more tests

* Allow +-30 seconds window for signed request to remain valid

* Disable time window validation for signed requests, restore 7 days
as PuSH subscription duration (which was previous default due to a bug)

Can be filtered by a specific domain
Resolves #2292