* Add handling of Linked Data Signatures in payloads
* Add a way to sign JSON, fix canonicalization of signature options
* Fix signatureValue encoding, send out signed JSON when distributing
* Add missing security context
* Ignore empty response in ActivityPub::FetchRemoteStatusService
This fixes `NoMethodError: undefined method `[]' for nil:NilClass` error.
* Check json.nil? in JsonLdHelper#supported_context?
- Tries to avoid performing HTTP request if the keyId is an actor URI
- Likewise if the URI is a fragment URI on top of actor URI
- Resolves public key, returns owner if the owner links back to the key
* 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
