Tag raw doesnt work with code snippets

[Zabuzard]

In some more complex setups, such as in the presence of code snippets and other, /tag-manage raw does not seem to work as expected.

As an example, use /tag-manage raw id: bfs:

It messes up the starting code snippet, the ending code snippets and also some of the bold-markers.

The raw content of this message, for testing purposes, is: https://pastebin.com/4tuEQ7Bz

[Zabuzard]

Found the issue. We use MarkdownSanitizer.escape but that escapes three backticks only with a single backslash but all three backticks need to be escaped for it to work properly.