Review extensions to be toggled in settings for Bonfire Classic 1.0

[ivanminutillo]

Related to #910

Proposal:

Toggable

• Reactions [unsure because there's not really point to have a classic flavours without reactions?]
• open science
• bonfire_label
• bonfire_open_id
• messages

Non Toggable

• UI for moderation
• UI for social graph
• UI for posts
• UI for messages
• bonfire_mailer
• bonfire_editor_milkdown
• search
• tag
• bonfire_files
• bonfire_invite_links
• classify
• bonfire_label
• bonfire_federate_ap
• social graph
• posts
• bonfire
• bonfire_poll [not ready yet]

[mayel]

Seems we're not thinking of extensions in quite the same way. IMO the only ones that should really be not possible to disable are common and boundaries. All others should be togglable/swappable (notably UI ones, for people wanting to use alternative UI implementation, or even to run Bonfire in headless mode, but also backend ones for features which are not needed).
But I see the point about avoiding a user (esp. when new to the software) accidentally disabling something and breaking the app in unexpected ways (though #718 should make sure things degrade gracefully), so a middle ground may be expanding the abilities of instance admins to control which extensions are togglable: https://github.com/bonfire-networks/bonfire-app/issues/990 (and each flavour could set defaults for those)