Block a user
WIP: 10c - adfToPlainMarkdown and plainMarkdownToAdf exported
WIP: Refuse a message past the held-message bound with ESME_RTHROTTLED, and answer a full reassembly buffer the same way
10b - plainMarkdownToAdf's ADF→ADF lift
WIP: 10b - plainMarkdownToAdf's ADF→ADF lift
10a - adfToPlainMarkdown's ADF→ADF reduction
Cap the heap unanswered messages hold, and detach them from the chunk they arrived in