arti-rpcserver: remove string slices

    /// Try to decode and validate `s` as a [`GlobalId`].

    ///

    /// Returns `Ok(None)` if `s` is not tagged as an identifier for a `GlobalId`.

    #[allow(clippy::string_slice)] // TODO

    pub(crate) fn try_decode(key: &MacKey, s: &ObjectId) -> Result<Option<Self>, LookupError> {

        use base64ct::{Base64Unpadded as B64, Encoding};

        if !s.as_ref().starts_with(GlobalId::TAG_CHAR) {

        let Some(remainder) = s.as_ref().strip_prefix(GlobalId::TAG_CHAR) else {

            return Ok(None);

        }

        };

        let mut bytes = [0_u8; Self::ENCODED_LEN];

        let byte_slice = B64::decode(&s.as_ref()[1..], &mut bytes[..])

            .map_err(|_| LookupError::NoObject(s.clone()))?;

        let byte_slice =

            B64::decode(remainder, &mut bytes[..]).map_err(|_| LookupError::NoObject(s.clone()))?;

        Self::try_decode_from_bytes(key, byte_slice)

            .ok_or_else(|| LookupError::NoObject(s.clone()))

            .map(Some)