common: Add `Deserialize` and `Serialize` to `Identifier`

[sebastinez]

I would benefit in radicle-client-services/http-api, if I could serialize and deserialize this enum from a string, IMO if we would check if it's only a prefix or a full git2::Oid we should be able to do just that. Am I missing something? Else would implement it in a PR.

https://github.com/radicle-dev/radicle-cli/blob/ea07d1c1327fd05e7792b771436744d415bf4fd9/common/src/cobs/shared.rs#L64

[cloudhead]

Yeah, the code is basically there already (FromStr and Display), do you specifically need serde support?

[sebastinez]

Closing this, since it's not relevant anymore