Use a Symfony Form for jury clarifications.

[nickygerritsen]

Also sanitize only after converting to markdown. Fixes #2311

[vmcj]

I've little experience with those forms.

[meisterT]

Code looks fine, feel free to merge. But I do have a couple more suggestions/nits (will write separate comments for each):

code blocks for teams do not look right in preview:

Once sent, it looks ok:

Interestingly enough the same works on the jury side:

[meisterT]

The reply button after starting a reply is useless and collapses the reply-form. I think it should be replaced by the "send" button:

[meisterT]

The reply form looks like a Matryoshka of boxes and clutter, remove at least these two:

Then "message" is unnecessary as there is only one text field and I don't see a use case to change the subject in a reply.

[nickygerritsen]

Note that your comments are all about the team clarification page, which I didn't even touch. I do agree with the remakrs so we should fix them for sure.