chore: add potential use cases documentation for ica (backport #2594)

docs/.vuepress/config.js

@@ -193,6 +193,11 @@ module.exports = {
                   directory: false,
                   path: "/apps/interchain-accounts/parameters.html",
                 },
+                {
+                  title: "Development Use Cases",
+                  directory: false,
+                  path: "/apps/interchain-accounts/development.html",
+                },
                 {
                   title: "Active Channels",
                   directory: false,

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

@@ -1,5 +1,5 @@
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-order: 5
+order: 6
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 # Understanding Active Channels 
@@ -29,4 +29,4 @@ The following is a list of issues which will provide the infrastructure to make
 - [IBC Channel Upgrades](https://github.com/cosmos/ibc-go/issues/1599)
 - [Implement ORDERED_ALLOW_TIMEOUT logic in 04-channel](https://github.com/cosmos/ibc-go/issues/1661)
 - [Add ORDERED_ALLOW_TIMEOUT as supported ordering in 03-connection](https://github.com/cosmos/ibc-go/issues/1662)
-- [Allow ICA channels to be opened as ORDERED_ALLOW_TIMEOUT](https://github.com/cosmos/ibc-go/issues/1663)
+- [Allow ICA channels to be opened as ORDERED_ALLOW_TIMEOUT](https://github.com/cosmos/ibc-go/issues/1663)

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

@@ -1,5 +1,5 @@
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-order: 6
+order: 7
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 # Building an authentication module

docs/apps/interchain-accounts/development.md

@@ -0,0 +1,36 @@
+<!--
+order: 5
+-->
+
+# Development use cases
+
+The initial version of interchain accounts allowed for the controller module to be extended by providing it with an underlying application which would handle all packet callbacks.
+That functionality is now being deprecated in favor of alternative approaches. 
+This document will outline potential use cases and redirect each use case to the appropriate documentation. 
+
+## Custom authentication 
+
+Interchain accounts may be associated with alternative types of authentication relative to the traditional public/private key signing. 
+If you wish to develop or use interchain accounts with a custom authentication module, we recommend you use ibc-go v6 or greater. 
+
+The custom authentication module should interact with the controller module via the [MsgServer](./messages.md).
+
+## Redirection to a smart contract
+
+It may be desirable to allow smart contracts to control an interchain account.
+To faciliate such an action, the controller module may be provided an underlying application which redirects to smart contract callers. 
+An improved design has been suggested in [ADR 008](https://github.com/cosmos/ibc-go/pull/1976) which performs this action via middleware. 
+
+Implementors of this use case are recommended to follow the ADR 008 approach.
+The underlying application may continue to be used as a short term solution for ADR 008 and the [legacy API](./auth-modules.md#registerinterchainaccount) should continue to be utilized in such situations. 
+
+## Packet callbacks
+
+If a developer requires access to packet callbacks for their use case, then they having the following options:
+
+1. Write a smart contract which is connected via an ADR 008 or equivalent IBC application (recommended).
+2. Use the controller's underlying application to implement packet callback logic.
+
+If the first case, the smart contract should use the [MsgServer](./messages.md).
+
+In the second case, the underlying application should use the [legacy API](./auth-modules.md#registerinterchainaccount).