Combine UserOrGroup/PublicKey req/resp types in request layer

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
```rust
#[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,
pub(crate) failed_ids: Vec,
}
```

In document_api/requests
```rust
#[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,
},
#[serde(rename_all = "camelCase")]
Group {
id: String,
master_public_key: Option,
},
}
```

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.