[Beta 8] Links missing attributes like target, rel

[jordanjay29]

This appears to be a regression bug (#247 or surprise implementation of flarum/issue-archive#382 ;) ) from Beta 7.x.

Demonstrated at discuss.flarum.org (for example):

<a href="https://github.com/flarum/core/blob/c34fcecf0380d130d1aeb0a5dc6155f07f885d87/src/Formatter/Formatter.php#L140">https://github.com/flarum/core/blob/c34fcecf0380d130d1aeb0a5dc6155f07f885d87/src/Formatter/Formatter.php#L140</a>

[clarkwinkelmann]

Wait... this means it's reverting this commit I made a while ago 4c55d27 #1432 and therefore will prevent configuring those link attributes via extensions.

Not sure if my commit was the cause of the issue (looks like it was then ?), but I don't think that simply reverting is wise here as we loose the extensibility option 😬

[tobyzerner]

Unfortunately switching the order was the cause of this regression. Fixing regressions comes at a higher priority than adding new extensibility features, thus the process is:

1. Revert the commit that caused the regression (i.e. revert back to beta 7 behaviour)
2. Release beta 8
3. Consider options to allow for extensibility without causing regression in beta 9. @clarkwinkelmann if you would be so kind as to create an issue I'll add it to the b9 milestone!

[clarkwinkelmann]

@tobscure of course you're right. I'll check out how to re-implement this correctly.