* Fix undefined method error in sidekiq
Body can be not nil but still be empty, which causes a
`NoMethodError: undefined method `[]' for nil:NilClass` further in the
code. This checks for an empty body to avoid the issue.
* Fix codeclimate issue
* No need to re-require sidekiq plugins, they are required via Gemfile
* Add derailed_benchmarks tool, no need to require TTY gems in Gemfile
* Replace ruby-oembed with FetchOEmbedService
Reduce startup by 45382 allocated objects
* Remove preloaded JSON-LD in favour of caching HTTP responses
Reduce boot RAM by about 6 MiB
* Fix tests
* Fix test suite by stubbing out JSON-LD contexts
* Do not default the format in ProviderDiscovery
The format should be determined when discovering, as it is in the current
implementation, and it is a flaw if it is not determined.
* Spec ProviderDiscovery
Renato "Lond" Cerqueira