Allow Users to React to a Bookmark to Recieve a Copy

Spun off of conversations in https://github.com/python-discord/seasonalbot/issues/338#issuecomment-578322144 and https://github.com/python-discord/seasonalbot/pull/340#pullrequestreview-348784550:

@kwzrd:

I’ve also seen a suggestion that the bot could listen for further clicks on its 📨 reaction, and dispatch the bookmark to those who click as well. This would be a super clean way to ask to be given the bm as well, although it may not be very obvious that it does that.

@AG4lyf made a good initial implementation in #340 that exposed some UX concerns:

@sco1:

Regarding the reaction by others to receive the same bookmark: the implementation details need to be discussed more before the feature is merged.

I don’t think it makes sense from a UX perspective to utilize the same reaction for multiple purposes when one of those purposes silently disappears after a timeout. This is already barely discoverable functionality, and with this implementation a user that does know of its existence doesn’t know if it has timed out or if it’s broken. A second emoji solves half of the problem, which might be sufficient.

Since this implementation discussion shouldn’t block the fix being implemented by #340, it has been removed from the scope of that PR.

Per discussions in Discord, the initial feeling is to provide a separate reaction to expose this functionality & keep it distinct from the bot’s feedback that the DM has been sent. 📌 or 📍 have been suggested.

Also to be discussed is whether or not this should be implemented as either:

• A wait_for reaction loop, with a timeout that removes the reaction
• An on_reaction_add event handler with a persistent cache that links the bookmark invocation message and the target message.

The former is simpler to implement & is what I’m leaning towards. The latter is more generic but will be trickier to implement in a way that prevents the file from growing too large & limit vectors for trolling.

The reaction emoji and reaction handling approach should be decided on prior to work being done.

[ChrisLovering]

I’d like to give this a go. Even though this is already approved, I just want to confirm my plans.

• When someone calls .bm on a message the bot will:
  • Send a DM as normal (with the same error embed if DMs are disabled)
  • Send 1-2 sentence embed explaining that you can react to the embed and also get sent a DM with a link
  • Add a 📌 emoji to the embed
  • Have a 5 min wait_for listening for 📌 reactions
  • On reaction, the bot will send the bookmark DM to the reactor
  • If the reactor has DMs closed, send the same error embed as above.

[Kronifer]

Oh! In that case, sounds good!!