Combine UserOrGroup/PublicKey req/resp types in request layer

[clintfred]

We have some identical or nearly identical types in the request layer that could be cleaned up and/or unified.

Note that

Examples:

In group_api/requests

#[derive(Deserialize, Debug)]
#[serde(rename_all = "camelCase")]
pub struct SuccessRes {
    pub(crate) user_id: UserId,
}

#[derive(Deserialize, Debug)]
#[serde(rename_all = "camelCase")]
pub struct FailRes {
    pub(crate) user_id: UserId,
    pub(crate) error_message: String,
}

#[derive(Deserialize, Debug)]
#[serde(rename_all = "camelCase")]
pub struct GroupUserEditResponse {
    pub(crate) succeeded_ids: Vec<SuccessRes>,
    pub(crate) failed_ids: Vec<FailRes>,
}

In document_api/requests

        #[derive(Deserialize, Debug)]
        #[serde(rename_all = "camelCase")]
        struct SuccessRes {
            pub(crate) user_or_group: UserOrGroupRes,
        }

        #[derive(Deserialize, Debug)]
        #[serde(rename_all = "camelCase")]
        struct FailRes {
            pub(crate) user_or_group: UserOrGroupRes,
            pub(crate) error_message: String,
        }

        #[derive(Deserialize, Debug)]
        #[serde(tag = "type", rename_all = "camelCase")]
        enum UserOrGroupRes {
            User { id: String },
            Group { id: String },
        }

#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
#[serde(rename_all = "camelCase")]
pub struct AccessGrant {
    pub(crate) user_or_group: UserOrGroupWithKey,
    #[serde(flatten)]
    pub(crate) encrypted_value: EncryptedOnceValue,
}

#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
#[serde(rename_all = "camelCase", tag = "type")]
pub enum UserOrGroupWithKey {
    #[serde(rename_all = "camelCase")]
    User {
        id: String,
        // optional because the resp on document create does not return a public key
        master_public_key: Option<PublicKey>,
    },
    #[serde(rename_all = "camelCase")]
    Group {
        id: String,
        master_public_key: Option<PublicKey>,
    },
}

Notice that UserOrGroupWithKey's master_public_key is optional to support the response coming back from Document create. Document access revoke and other group apis may also be using similar types.