Rust client library and plugable databroker cli

[lukasmittag]

This PR addresses the need of a client library for rust for the new API (kuksa.val.v1) and makes the databroker-cli plugable.

To try this PR you need to know that per default it will be built with the old API client lib. If you want to use the new one use

cargo run --bin databroker-cli 

or

cargo run --bin databroker-cli --protocol kuksa-val-v1

[erikbosch]

How does Rust compiler handle features? Does it ignore features not included (like old fashioned #ifdef) or does it anyway compile them even if it does not include them in result.

If it ignore it totally - would it then be an idea to extend our CI so that it also builds the "feature_kuksa" variant, to make sure that we do not introduce any regressions that can be detected at compile time, i.e. that all code is compiled by CI.

[lukasmittag]

How does Rust compiler handle features? Does it ignore features not included (like old fashioned #ifdef) or does it anyway compile them even if it does not include them in result.

If it ignore it totally - would it then be an idea to extend our CI so that it also builds the "feature_kuksa" variant, to make sure that we do not introduce any regressions that can be detected at compile time, i.e. that all code is compiled by CI.

Yes that needs to be added. Good point!

[lukasmittag]

cargo clippy --all-targets --no-default-features --features feature_kuksa -- -W warnings -D warnings

would this be enough or would you actually fully build it

[erikbosch]

As part of the release I replaced most instances of this line with "Eclipse KUKSA Project" after a discussion with Sebastian. Could be good to do that also for the new files

[SebastianSchildt]

I agree, can we change this @lukasmittag ?

[lukasmittag]

Done @SebastianSchildt