Noting @rfcbot concerns before PFCP has started

[Centril]

Might be nice for team members to be able to note concerns they have when they first read an RFC before some other team member decides to @rfcbot fcp merge/close/postpone a proposal so that they save some time.

Context: https://github.com/rust-lang/rfcs/pull/2442#issuecomment-389652120

[anp]

I think this definitely could be good, although probably makes the data model a bit more complicated.

I have not fully thought through the impact it may have on how conversations work. For one thing, many RFCs change substantially in between initially being posted and when FCP occurs. I can also see the discussion changing drastically from a team member registering a blocking concern before it's been discussed with other team members.

cc @aturon

[Centril]

although probably makes the data model a bit more complicated.

So I was thinking that you'd add another table top_concern to the schema and it would be per issue... Then, the bot would take those into account when rendering things and checking if an RFC can make progress or not.