Update ActivityPub documentation

[trwnh]

Added more details in several places.

Preview: https://activitypub--mastodocs.netlify.app/spec/activitypub/

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[ClearlyClaire]

I'm a bit uneasy with the mention of search engines and such, as the scope of this setting was historically just for the profile directory, and is vaguely-defined.

[trwnh]

the description here is unchanged since 2019, i just moved it up from lower in the page (red line 521 in this changeset).

aside from that, it is worth noting that the current definition also says it is applied on "objects" without specifying that mastodon only applies it on actors. the wording is indeed vague, but i believe the original mention of "search engines and indexing tools" was just a generalization of the profile directory (which is an "internal" discovery service). you could envision a "search for profiles" service that would let you find discoverable accounts in a way similar to the profile directory, but with more details like including their bio and featured hashtags. but it doesn't really make sense to define this property only for actors even if it only gets used on actors.

the real contention to me is in whether this account-level preference carries over to posts. i think it generally does not, and therefore i avoided saying this (although i can see how it is still vague). relatedly, this is why i think discoverable should be attached to posts as well: to remove that kind of ambiguity. if we attach discoverable at the post level, you no longer need to check the account property. regardless, we might still (may or may not) consider a policy of deferring to the account property if the post doesn't declare whether it is discoverable. this basically creates the following states:

• if the post is discoverable: true, it SHOULD be shown in discovery features
• if the post is discoverable: false, it MUST NOT be shown in discovery features
• if the post is discoverable: null or the property is missing:
  • if the account is discoverable: true, the post MAY be shown in discovery features
  • if the account is discoverable: false, the post SHOULD NOT be shown in discovery features
  • if the account is discoverable: null or the property is missing, the post MAY be shown in discovery features if some other mechanism establishes consent, but SHOULD NOT be shown in lieu of any other mechanism

[trwnh]

@ClearlyClaire addressed everything except for the bit about discoverable. should i clarify that the indicator can be applied to account search instead of just saying "search"? something like this:

• toward being included -> toward having their account being included
• add the following line:

Note that an account being marked discoverable does not imply anything about their posts. Future changes in Mastodon may allow users to mark their posts discoverable as well.