Merge branch 'amiranda/99-refactor-rpc-implementation-of-admire-register_pfs_storage' into 'main'

Resolve "Refactor RPC implementation of `admire::register_pfs_storage`"

This MR moves the implementation of the RPC construction for
`ADM_register_pfs_storage` to `admire::detail` in `impl.[ch]pp`
similarly to other RPCs already refactored. This includes changing
the C ADM_types to native C++ types.

Closes #99

See merge request !68