feat: add /v2/micro-blocks/:hash/txs endpoint

[sborrazas]

refs #888

[jyeshe]

Looking neat for me. Some proposals on performance, response structure and testing.

[jyeshe]

Same reasoning as #898 (comment)

The proposed change is to add this to AeMdw.Node.Db:

  def micro_block_index(hash), do: micro_block_counter(hash, -1)

  defp micro_block_counter(hash, acc) do
    with block <- :aec_db.get_block(hash),
         :micro <- :aec_blocks.type(block) do
      micro_block_counter(:aec_blocks.prev_hash(block), acc + 1)
    else
      :key -> acc
    end
  end

and use micro_block_index(hash) instead of calling Db.get_micro_blocks() |> Enum.count()

Similar to:

defp micro_block_walker(hash) do
    with block <- :aec_db.get_block(hash),
         :micro <- :aec_blocks.type(block) do
      {block, :aec_blocks.prev_hash(block)}
    else
      :key -> nil
    end
  end

but without accumulating all previous micro blocks and transactions.

[sborrazas]

Discussed in previous PR

[jyeshe]

The fields related to the block could be moved to an upper level to avoid repeating them for all transactions.

[thepiwo]

if this is how the core node exposes the data, then I suggest to keep it as it is

[jyeshe]

okay, similar to here: https://api-docs.aeternity.io/#/external/GetMicroBlockTransactionsByHash

could you share the reason behind replicating a similar node's structure? it's not 100% the same.

[jyeshe]

Could we have some real fields to validate the rendering at least for the format and values that are not serialized with Node's serialize_for_client?

[sborrazas]

Ended up adding integration tests because I had to much so many node functions that the test became pointless