feat: add /pallets/errors

[marshacb]

Summary: An endpoint that returns the errors for a given pallet

/pallets/{palletId}/errors

Query Params

• at: Which block to query, it will default to the latest finalized block. Accepts a hash or blocknumber
• onlyIds: boolean to return only the Ids of each error instead of the entirety of each error

Sample response for /pallets/democracy/errors?onlyIds=true

{
	"at": {
		"hash": "0x6970f8f6d53d2386f50b4360f9b3bad80bb53181bdd22ed9e4333ab9e425beb8",
		"height": "13670232"
	},
	"pallet": "democracy",
	"palletIndex": "14",
	"items": [
		"ValueLow",
		"ProposalMissing",
		"AlreadyCanceled",
		"DuplicateProposal",
		"ProposalBlacklisted",
		"NotSimpleMajority",
		"InvalidHash",
		"NoProposal",
		"AlreadyVetoed",
		"DuplicatePreimage",
		"NotImminent",
		"TooEarly",
		"Imminent",
		"PreimageMissing",
		"ReferendumInvalid",
		"PreimageInvalid",
		"NoneWaiting",
		"NotVoter",
		"NoPermission",
		"AlreadyDelegating",
		"InsufficientFunds",
		"NotDelegating",
		"VotesExist",
		"InstantNotAllowed",
		"Nonsense",
		"WrongUpperBound",
		"MaxVotesReached",
		"TooManyProposals",
		"VotingPeriodLow"
	]
}

/pallets/{palletId}/errors/{errorItemId}

Query Params

• at: Which block to query, it will default to the latest finalized block. Accepts a hash or blocknumber
• metadata: boolean to choose whether to include an errors metadata in the response

Sample response for /pallets/democracy/errors/ValueLow

{
	"at": {
		"hash": "0xc2550d0da7f0ad271045c201156d7cce4aa6fd461c7f1812269e763af8f6f7e1",
		"height": "13670213"
	},
	"pallet": "democracy",
	"palletIndex": "14",
	"errorItem": "valueLow"
}

[TarikGul]

@marshacb Can you please include a detailed description in the PR about the feature, it's a bit easier to digest and compare what is expected.

[TarikGul]

So overall, really great PR. Just want to get your thoughts on some of the questions below. Also if we should make some sort of AbstractPalletsService for some of the logic below if it's to be reused.

[TarikGul]

One more addition as well, let's add these endpoint to e2e-tests/latest/endpoints/polkadot.ts.

[TarikGul]

Great job, just some small nits. 👍

[Imod7]

Looks Great to me! 💯