MP-3296 pagination

[piobab]

Common way to do pagination in Cosmwasm is using limit, start_after and respond with vector of data. For example:

// settings for pagination
const MAX_LIMIT: u32 = 30;
const DEFAULT_LIMIT: u32 = 10;

pub fn query_list_members(
    deps: Deps,
    start_after: Option<String>,
    limit: Option<u32>,
) -> StdResult<MemberListResponse> {
    let limit = limit.unwrap_or(DEFAULT_LIMIT).min(MAX_LIMIT) as usize;
    let addr = maybe_addr(deps.api, start_after)?;
    let start = addr.as_ref().map(Bound::exclusive);

    let members = MEMBERS
        .range(deps.storage, start, None, Order::Ascending)
        .take(limit)
        .map(|item| {
            item.map(|(addr, weight)| Member {
                addr: addr.into(),
                weight,
            })
        })
        .collect::<StdResult<_>>()?;

    Ok(MemberListResponse { members })
}

As an API user if I want to know if there is more data:

• check if responded number of elements is less than sent limit parameter. This is problematic because if I send limit > MAX_LIMIT I get less elements than requested - thinking that there is no more data.
• execute next query and see if there is more data. This is not efficient because I make extra query.
  Moreover, it is easy to forget about pagination as we noticed during contract configuration / validation. You could query something and you basically use default pagination params and don't see the rest of elements.

Solution
Add metadata data

#[cw_serde]
pub struct PaginationResponse<T> {
    pub data: Vec<T>,
    pub metadata: Metadata,
}

#[cw_serde]
pub struct Metadata {
    pub has_more: bool,
    pub next_start_after: Option<String>,
}

This way we see in the response if there is more data. Easy to operate on without depending on default params.

[piobab]

This PR will be used to fix issue no. 5 from Oak.

[thec00n]

@piobab is there already a PR that fixes the audit issue on the rover side?

[piobab]

@piobab is there already a PR that fixes the audit issue on the rover side?

mars-protocol/rover#191