* start centralizing negotiation logic for API
* swagger document nodeinfo endpoint
* go fmt
* document negotiate function
* use content negotiation
* tidy up negotiation logic
* negotiate content throughout client api
* swagger
* remove attachment on Content
* add accept header to test requests
* reference logrus' global logger instead of passing and storing a logger reference everywhere
* always directly use global logrus logger instead of referencing an instance
* test suites should also directly use the global logrus logger
* rename gin logging function to clarify that it's middleware
* correct comments which erroneously referenced removed logger parameter
* setting log level for tests now uses logrus' exported type instead of the string value, to guarantee error isn't possible
Inbox POST from federated servers now working for statuses and follow requests.
Follow request client API added.
Start work on federating outgoing messages.
Other fixes and changes/tidying up.
