Add message and rpc handler to recover clients using v1 governance proposals

[crodriguezvega]

Part of #1282.

Overview of changes:

Protobuf

• Add a new rpc handler to 02-client MsgService. Something like this:

rpc RecoverClient(MsgRecoverClient) returns (MsgRecoverClientResponse);

where MsgRecoverClient could look like this:

message MsgRecoverClient {
  option (gogoproto.equal)           = false;
  option (gogoproto.goproto_getters) = false;
  option (cosmos.msg.v1.signer)      = "authority";

  // authority is the address of the governance account.
  string authority = 1;
  // the client identifier for the client to be updated if the proposal passes
  string subject_client_id = 2;
  // the substitute client identifier for the client standing in for the subject
  // client
  string substitute_client_id = 3;
}

and MsgRecoverClientResponse can be empty:

message MsgRecoverClientResponse {}

02-client

• Add function RecoverClient to 02-client keeper with logic to recover client. The signature of the function could look like this:

func (k Keeper) RecoverClient(ctx sdk.Context, subjectClientId, substituteClientId string) error

• Add implementation of RecoverClient, which could be similar to ClientUpdateProposal's implementation.

• Implement sdk.Msg interface for MsgRecoverClient.

• If it's possible to re-use the error code for ErrInvalidUpdateClientProposal, then rename the error to, for example, ErrInvalidRecoveryClient and adjust the error description to invalid recovery client.

Core

• Add implementation of RecoverClient rpc handler in IBC core msg_server.go (modules/core/keeper/msg_server.go). The signature of the handler could look like this:

func (k Keeper) RecoverClient(
  goCtx context.Context, 
  msg *clienttypes.MsgRecoverClient
) (*clienttypes.MsgRecoverClientResponse, error)

and the implementation could look like this:

// check message signer matches authority set
if k.authority != msg.Signer {
  return nil, errorsmod.Wrapf(
    govtypes.ErrInvalidSigner, 
    "invalid authority: expected %s, got %s", k.authority, msg.Signer
  )
}

ctx := sdk.UnwrapSDKContext(goCtx)

err := k.ClientKeeper.RecoverClient(ctx, msg.SubjectClientId, msg.SubstituteClientId)
if err != nil {
  return nil, errorsmod(err, "client recovery failed")
}

return &types. MsgRecoverClientResponse{}, nil

• Add extra &MsgRecoverClient{} as input to RegisterImplementations.

CLI

• Implement a CLI command (NewCmdSubmitClientRecoverProposal) in 02-client with flag recover-client and parameters subject-client-id and substitute-client-id to construct a MsgRecoverClient and include it in a MsgSubmitProposal. Use v1beta1 legacy NewCmdSubmitUpdateClientProposal command and SDK's NewCmdSubmitUpgradeProposal as examples.

Documentation

• Update the documentation for client recovery via governance proposals.

Break up the implementation in multiple PRs. One possible suggestion:

• Add proto message, skd.Msg implementation for RecoverClient #4493
• Add Recover client handler in 02-client #4498
• Add message server handler for recovering a client #4500
• Add e2e for recovering a client #4530
• Update docs for recovering a client using v1 gov proposals #4584
• Add CLI command for sumbitting a Recover Client proposal #4521

[colin-axner]

Closed by all the linked issues!