Proper Markdown message building

[ulfsauer0815]

Building markdown messages consists of a few convenience functions that simply concatenate strings in a very inefficient manner.
This can be improved (readability, performance etc.), maybe Blaze has some interesting ideas?

[ulfsauer0815]

It might be possible to make message shortening smarter if it can work on an AST - shortening only the displayed content without touching the markup if possible.
This way we would actually shorten the displayed content and not mangle the markup which leads to broken/no markup.

Not considering markup within the message yet, which would require parsing markdown and also make the shortening logic more complicated.

The content size can still not be calculated accurately, e.g. when images are embedded.