"Send/Post to conversation": Add an input field for a message

I like the feature a lot and I actually prefer it to adding comments to a card. When referencing someone in a comment, the notification just shows the AD-User's GUID and most of the time nobody responds. When posting the card to a conversation instead, people know for sure that their action is needed.

Most of the time when posting a card to a conversation, I want to add some context though. For now, I have to open the card, click "post to conversation", select the recipient, go to Talk, open the conversation I posted to, send an additional message where I describe the context and then I go back to Deck and continue my work.

It would be far easier when I select "post to conversation" and could directly write that message in the lower half of the conversation selection window before clicking the confirmation button. Additionally, I would like to see #3180 implemented. Having to open the card every time I want to send it (and move the cursor to a totally different area of the screen!) makes it much more cumbersome than it should be.

Start by tracing the Deck action labeled “post to conversation” and the conversation selection window described in the issue; also review related issue #3180. Done means the selection flow accepts context text and sends it with the card to the chosen conversation without requiring a separate Talk step.