docs: document that version string can be empty as argument of Regist…

…erInterchainAccount (cosmos#1582)

Co-authored-by: Carlos Rodriguez <crodveg@gmail.com>

docs/apps/interchain-accounts/active-channels.md

@@ -12,11 +12,11 @@ channel type that provides ordering of packets without the channel closing on ti
 When an Interchain Account is registered using the `RegisterInterchainAccount` API, a new channel is created on a particular port. During the `OnChanOpenAck` and `OnChanOpenConfirm` steps (controller & host chain) the `Active Channel` for this interchain account
 is stored in state.
 
-It is possible to create a new channel using the same controller chain portID if the previously set `Active Channel` is now in a `CLOSED` state. This channel creation can be initialized programatically by sending a new `OnChanOpenInit` message like so:
+It is possible to create a new channel using the same controller chain portID if the previously set `Active Channel` is now in a `CLOSED` state. This channel creation can be initialized programatically by sending a new `MsgChannelOpenInit` message like so:
 
 ```go
-	msg := channeltypes.NewMsgChannelOpenInit(portID, string(versionBytes), channeltypes.ORDERED, []string{connectionID}, icatypes.PortID, icatypes.ModuleName)
-	handler := k.msgRouter.Handler(msg)
+msg := channeltypes.NewMsgChannelOpenInit(portID, string(versionBytes), channeltypes.ORDERED, []string{connectionID}, icatypes.PortID, icatypes.ModuleName)
+handler := k.msgRouter.Handler(msg)
 ```
 
 Alternatively, any relayer operator may initiate a new channel handshake for this interchain account once the previously set `Active Channel` is in a `CLOSED` state. This is done by initiating the channel handshake on the controller chain using the same portID associated with the interchain account in question.  

docs/apps/interchain-accounts/auth-modules.md

@@ -38,15 +38,15 @@ func (im IBCModule) OnChanOpenInit(
     chanCap *capabilitytypes.Capability,
     counterparty channeltypes.Counterparty,
     version string,
-) error {
+) (string, error) {
     // the authentication module *must* claim the channel capability on OnChanOpenInit
     if err := im.keeper.ClaimCapability(ctx, chanCap, host.ChannelCapabilityPath(portID, channelID)); err != nil {
-        return err
+        return version, err
     }
 
     // perform custom logic
 
-    return nil
+    return version, nil
 }
 
 // OnChanOpenAck implements the IBCModule interface
@@ -157,7 +157,7 @@ if err := keeper.icaControllerKeeper.RegisterInterchainAccount(ctx, connectionID
 return nil
 ```
 
-The `version` argument is used to support ICS29 fee middleware for relayer incentivization of ICS27 packets. Consumers of the `RegisterInterchainAccount` are expected to build the appropriate JSON encoded version string themselves and pass it accordingly.
+The `version` argument is used to support ICS29 fee middleware for relayer incentivization of ICS27 packets. Consumers of the `RegisterInterchainAccount` are expected to build the appropriate JSON encoded version string themselves and pass it accordingly. If an empty string is passed in the `version` argument, then the version will be initialized to a default value in the `OnChanOpenInit` callback of the controller's handler, so that channel handshake can proceed.
 
 The following code snippet illustrates how to construct an appropriate interchain accounts `Metadata` and encode it as a JSON bytestring:
 

docs/migrations/v3-to-v4.md

@@ -30,7 +30,7 @@ The return signature now includes the application version as detailed in the lat
 
 The `RegisterInterchainAccount` API has been modified to include an additional `version` argument. This change has been made in order to support ICS29 fee middleware, for relayer incentivization of ICS27 packets.
 Consumers of the `RegisterInterchainAccount` are now expected to build the appropriate JSON encoded version string themselves and pass it accordingly. 
-This should be constructed within the interchain accounts authentication module which leverages the APIs exposed via the interchain accounts `controllerKeeper`. 
+This should be constructed within the interchain accounts authentication module which leverages the APIs exposed via the interchain accounts `controllerKeeper`. If an empty string is passed in the `version` argument, then the version will be initialized to a default value in the `OnChanOpenInit` callback of the controller's handler, so that channel handshake can proceed.
 
 The following code snippet illustrates how to construct an appropriate interchain accounts `Metadata` and encode it as a JSON bytestring: