Fix #830: Better handling of follow/accept messages to avoid and recover from desync between instances

Fix #737: delivering of local activities causing unintended side effects, such as rollbacking changes

Fix #737: delivering of local activities causing unintended side effects, such as rollbacking changes

Ensures federation urls can answer to application/ld+json, application/activity+json and application/json requests

Fix #706: Added a 'fix_federation_ids' management command to deal with protocol/domain issues in federation
IDs after deployments