* Add limit on inbox payload size
The 1MB limit is consistent with the limit we use when fetching remote resources
* Add limit to number of options from federated polls
* Add a limit to the number of federated profile fields
* Add limit on federated username length
* Add hard limits for federated display name and account bio
* Add hard limits for `alsoKnownAs` and `attributionDomains`
* Add hard limit on federated custom emoji shortcode
* Highlight most destructive limits and expand on their reasoning
Some ActivityPub projects have a FEDERATION.md which is used to describe the
various extensions they use.
Everything here is also documented elsewhere, but it's a concise starting point
with links to that documentation.
