R CMD check found WARNINGs

Process completed with exit code 1.

Input 'save-always' has been deprecated with message: save-always does not work as intended and will be removed in a future release. A separate `actions/cache/restore` step should be used instead. See https://github.com/actions/cache/tree/main/save#always-save-cache for more details.

Undocumented arguments in Rd file 'compensator_differences.Rd'

Non-portable flags in variable 'PKG_CXXFLAGS':

Found the following file(s) containing GNU extensions:

File 'stelfi/libs/x64/stelfi.dll':

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/