Fix codec issue for dense-pull-ledger-diff

[Dengjianping]

Signed-off-by: Dengjianping djptux@gmail.com

Description

The workaround is that I implement From trait for DensePullResponse.

impl From<PullResponse> for DensePullResponse {
    #[inline]
    fn from(resp: PullResponse) -> DensePullResponse {
        Self {
            should_continue: resp.should_continue,
            receivers: base64::encode(resp.receivers.encode()),
            senders: base64::encode(resp.senders.encode()),
            senders_receivers_total: resp.senders_receivers_total,
            next_checkpoint: None,
        }
    }
}

When client api calls runtime api, PullResponse will be converted into DensePullResponse.

#[async_trait]
impl<B, C> PullApiServer for Pull<B, C>
where
    B: Block,
    C: 'static + ProvideRuntimeApi<B> + HeaderBackend<B>,
    C::Api: PullLedgerDiffApi<B>,
{
    #[inline]
    fn dense_pull_ledger_diff(
        &self,
        checkpoint: Checkpoint,
        max_receivers: u64,
        max_senders: u64,
    ) -> RpcResult<DensePullResponse> {
        let api = self.client.runtime_api();
        let at = BlockId::hash(self.client.info().finalized_hash);
        api.pull_ledger_diff(&at, checkpoint.into(), max_receivers, max_senders)
            .map(Into::into) // PullResponse to DensePullResponse
            .map_err(|err| {
                CallError::Custom(ErrorObject::owned(
                    PULL_LEDGER_DIFF_ERROR,
                    "Unable to compute dense state diff for pull",
                    Some(format!("{err:?}")),
                ))
                .into()
            })
    }
}

Now the response will be returned correctly.

{
  should_continue: false,
  receivers: 'J0vqVrFQV45G3bIfUnzxdKGRsPRjkbhqScQf0WmosgRP8vqVpKI5YlkgM8468+rxNqpE..`
  senders: 'AA==',
  senders_receivers_total: '0x02000000000000000000000000000000',
  next_checkpoint: null
}

So the runtime api dense_pull_ledger_diff can be removed, RuntimeDensePullResponse is not necessary anymore.
code is more cleaner.

closes #979

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Situational Notes:

• If adding functionality, write unit tests!
• If importing a new pallet, choose a proper module index for it, and allow it in BaseFilter. Ensure every extrinsic works from front-end. If there's corresponding tool, ensure both work for each other.
• If needed, update our Javascript/Typescript APIs. These APIs are officially used by exchanges or community developers.
• If modifying existing runtime storage items, make sure to implement storage migrations for the runtime and test them with try-runtime. This includes migrations inherited from upstream changes, and you can search the diffs for modifications of #[pallet::storage] items to check for any.

[Dengjianping]

I will submit typescript based client test cases in another pr soon once this pr gets merged.

[ghzlatarev]

@Dengjianping description please.

[flame4]

Cool solution!

[Dengjianping]

@Dengjianping description please.

Added.

[Garandor]

LGTM except for the test failure

[ghzlatarev]

LGTM , the unit tests should pass after #981 is merged.