fix(builtin-function): fix string conversion of years-months-durations

[s-frick]

Description

• fix string conversion of years-months-durations
• add tests for string conversion of zero-length years-months-duration
• add tests for string conversion of negative years-months-duration

Related issues

closes #631

[s-frick]

@saig0 The Clirr API check is failing at the moment. Do you have advice how to fix this or is it a false-positive?

[saig0]

@sebi87 thank you for contributing again. :tada:

You can ignore the Clirr errors. This is a false positive. I'll take care of Clirr. :+1:

[saig0]

@sebi87 I updated the Clirr config (https://github.com/camunda/feel-scala/pull/639). If you rebase, the build should pass now.

[saig0]

/backport

[github-actions[bot]]

Backport failed for 1.15, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin 1.15
git worktree add -d .worktree/backport-636-to-1.15 origin/1.15
cd .worktree/backport-636-to-1.15
git checkout -b backport-636-to-1.15
ancref=$(git merge-base 017ae36a8cff04be1ef24c09cbc611bfdbb0626f b39c66476372aa8bef19863bd63f7dd8cf17d409)
git cherry-pick -x $ancref..b39c66476372aa8bef19863bd63f7dd8cf17d409

[github-actions[bot]]

Backport failed for 1.16, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin 1.16
git worktree add -d .worktree/backport-636-to-1.16 origin/1.16
cd .worktree/backport-636-to-1.16
git checkout -b backport-636-to-1.16
ancref=$(git merge-base 017ae36a8cff04be1ef24c09cbc611bfdbb0626f b39c66476372aa8bef19863bd63f7dd8cf17d409)
git cherry-pick -x $ancref..b39c66476372aa8bef19863bd63f7dd8cf17d409