infill : add new example + extend server API (#3296)

* vvhg-code-infill (#1)

* infill in separate example (#2)

* reverted changes to main and added infill example

* cleanup

* naming improvement

* make : add missing blank line

* fix missing semicolon

* brought infill up to current main code

* cleanup

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Co-authored-by: Cebtenzzre <cebtenzzre@gmail.com>