fix: no longer crash on extensions-ception

[ndrsg]

fix handling of extensions-tags inside extensions-tags by counting the depth

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[lnicola]

Can you please squash if it's not too much of a hassle?

[ndrsg]

sure :)

[urschrei]

Just want to note that I very much enjoyed "extensions-ception"

[lnicola]

I can't check right now, but can there be two closing tags for only one opening tag? What happens in that case?

[ndrsg]

1 opening followed by 2 closing tags:

This extensions-consume function would exit on the first closing tag without error.

This would lead to the outer logic to receive a extensions-closing tag. Depends if this case is handled there.

Might happen with other non-gpx-tags inside an extensions-block as well.

[lnicola]

But there's no code to return out of the function when the depth reaches 0. The old version used to do that.

[ndrsg]

I will have a look tomorrow.

Another option might be recursion instead of counting depth?

[ndrsg]

soo.. I changed the approach a bit and oriented on the other implementations, also keeping in mind a future implementation of parsing the extensions content into a structure with kind of "generic parser"?

also added some tests, where I would expect errors. turned out, that the xmlreader already tests the xml-structure quite well.

now treating "extensions"-tags inside an "extensions"-block just like any other tag, hence its just coincidence, if an internal tag is called "extensions", right?