Implement canonicals

[theErikss0n]

Reason (Why?)
We can improve SEO with this.
(Content should only be accessible by one url)[https://de.ryte.com/wiki/Canonical_Tag] which is not the case on our site, as content can be accessed regardless of casing or trailing slashes.

Solution (What?)
Ensure there is a canonical for every url.

Out of scope
Our resultpages are generated and don't need this.