implement getStateValidators in lodestar-validator

[3xtr4t3rr3str14l]

resolve #2232, #2235, and #2293 by implementing getStateValidators on the lodestar-validator client API side and then use that inside updateValidators()

[codeclimate]

Code Climate has analyzed commit 1c52b59 and detected 4 issues on this pull request.

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Category	Count
Complexity	4

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[wemeetagain]

We want to update getStateValidators to accept an array of validator indices/pubkeys (

lodestar/packages/lodestar-validator/src/api/impl/rest/beacon/state.ts

Line 10 in 4f19c79

async getStateValidator(

)
(using https://ethereum.github.io/eth2.0-APIs/#/Beacon/getStateValidators), and then only call that once in updateValidators

[3xtr4t3rr3str14l]

We want to update getStateValidators to accept an array of validator indices/pubkeys (

lodestar/packages/lodestar-validator/src/api/impl/rest/beacon/state.ts

Line 10 in 4f19c79

async getStateValidator(

)
(using https://ethereum.github.io/eth2.0-APIs/#/Beacon/getStateValidators), and then only call that once in updateValidators

for the request you linked (from the eth2 api docs), that would return all the validators for the whole state. the other similar call is this one, which just gets one validator per id:
https://ethereum.github.io/eth2.0-APIs/#/Beacon/getStateValidator

so in order to stay within the spec, wouldn't we just call getStateValidator in batch like i'm doing here? (since i'm assuming we don't want to fetch the whole state validators every time we run updateValidators). Or do you think it's better to deviate from the spec in this case?

[wemeetagain]

The getStateValidators request has an id param that takes an array of validator indices/pubkeys, used to filter the response to only the validators provided.

[3xtr4t3rr3str14l]

The getStateValidators request has an id param that takes an array of validator indices/pubkeys, used to filter the response to only the validators provided.

ah gotcha, i didn't see that. i'll restructure this PR accordingly