added graphhopper sample

[karussell]

this adds a new graphhopper sample using the more powerful POST /navigate request. This is the same request format as POST /route but with the mapbox compatible response.

Also graphhopper can be used for the multiplatform sample via changing provider="valhalla" to "graphhopper".

Related to #151 (comment)

Not sure why the test / build fails here, but locally ./gradle clean build is green.

(Please note that I'm not a good Android/Kotlin dev and let me know possible improvements :) )

[Fabi755]

Is there a demo server, that is working without a key. Do you know that?

[karussell]

I'm not aware of one. But there are two options:

1. we can provide a demo API key with a certain limited request count per day and
2. users could setup a GraphHopper server on their own.

[Fabi755]

For the sample in the app folder, please add the new configurations to our gradle script, that generated on first build. Here the URLs can changed.

I suggest that we add only one URL string (graphhopper_url) instead of two ones (url + key).

And would very happy if we having a sample URL, that is working out of the box. So your idea with a limited key would be enough 👍
Changing the URL on both places:

• Default value generated by gradle script
• Directly in new sample project

Finally, please add a CHANGELOG entry. You can copy it from the valhalla one.

Thanks for your PR 💙 💙 💙

[karussell]

Thanks!

Can you have a look if the latest commit fixes what you meant?

[Fabi755]

Thank you 💙

[karussell]

Thanks!