Fix Signing Infos Endpoint

[alexanderbez]

• Fix pagination in /slashing/signing_infos
• Use querier instead of RPC call (which always limited it to the 100 max validators)
• Use querier for /slashing/validators/{validatorPubKey}/signing_info

closes: #4194

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• Wrote tests

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[codecov]

Codecov Report

Merging #4292 into master will increase coverage by 0.24%.
The diff coverage is 21.73%.

@@            Coverage Diff             @@
##           master    #4292      +/-   ##
==========================================
+ Coverage    59.1%   59.35%   +0.24%     
==========================================
  Files         217      214       -3     
  Lines       14595    14526      -69     
==========================================
- Hits         8627     8622       -5     
+ Misses       5330     5266      -64     
  Partials      638      638

[alessio]

ACK

[fedekunze]

so there's a good practice in returning OK 200 even if the response is empty, because the request was processed successfully. See https://stackoverflow.com/a/13367198

[alexanderbez]

Hmmm, ok so for collections, this makes sense. But this is a single resource you're looking for, not a collection. If I go with this approach and just return a 200 OK with an empty ValidatorSigningInfo{} object, you'll get the following as a response:

{
    "address": "",
    "index_offset": "0",
    "jailed_until": "0001-01-01T00:00:00Z",
    "missed_blocks_counter": "0",
    "start_height": "0",
    "tombstoned": false
}

This isn't what I'd want to see as an API consumer. Or am I wrong? I suppose I can add omitempty to all the JSON tags so you'll get {} as a response. Is that better?

[fedekunze]

ditto, no need for this error if the request is successful

[alexanderbez]

Responded; see above.

[rigelrozanski]

looks good - only one restructure per comment