docs(staking): add cancel-unbond delegations spec (#11473)

## Description

Closes: #XXXX

related to #10885 



---

### Author Checklist

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I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -264,7 +264,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * [\#11011](https://github.com/cosmos/cosmos-sdk/pull/11011) Remove burning of deposits when qourum is not reached on a governance proposal and when the deposit is not fully met. 
 * [\#11019](https://github.com/cosmos/cosmos-sdk/pull/11019) Add `MsgCreatePermanentLockedAccount` and CLI method for creating permanent locked account
 * (x/staking) [\#10885] (https://github.com/cosmos/cosmos-sdk/pull/10885) Add new `CancelUnbondingDelegation`
-  transaction to `x/staking` module. Delegators can now cancel unbonding delegation entry and re-delegate back to validator.
+  transaction to `x/staking` module. Delegators can now cancel unbonding delegation entry and delegate back to validator.
 * (x/feegrant) [\#10830](https://github.com/cosmos/cosmos-sdk/pull/10830) Expired allowances will be pruned from state.
 * (x/authz,x/feegrant) [\#11214](https://github.com/cosmos/cosmos-sdk/pull/11214) Fix Amino JSON encoding of authz and feegrant Msgs to be consistent with other modules.
 * (authz)[\#11060](https://github.com/cosmos/cosmos-sdk/pull/11060) Support grant with no expire time.

x/staking/spec/02_state_transitions.md

@@ -91,6 +91,12 @@ Delegation may be called.
   shares from the `BondedPool` to the `NotBondedPool` `ModuleAccount`
 * remove the validator if it is unbonded and there are no more delegation shares.
 
+### Cancel an `UnbondingDelegation` Entry 
+When a `cancel unbond delegation` occurs both the `validator`, the `delegation` and an `UnbondingDelegationQueue` state will be updated.
+* if cancel unbonding delegation amount equals to the `UnbondingDelegation` entry `balance`, then the `UnbondingDelegation` entry deleted from `UnbondingDelegationQueue`.
+* if the `cancel unbonding delegation amount is less than the `UnbondingDelegation` entry balance, then the `UnbondingDelegation` entry will be updated with new balance in the `UnbondingDelegationQueue`. 
+* cancel `amount` is [Delegated](02_state_transitions.md#delegations) back to  the original `validator`.
+
 ### Complete Unbonding
 
 For undelegations which do not complete immediately, the following operations

x/staking/spec/03_messages.md

@@ -116,6 +116,27 @@ When this message is processed the following actions occur:
 
 ![Unbond sequence](../../../docs/uml/svg/unbond_sequence.svg)
 
+## MsgCancelUnbondingDelegation
+The `MsgCancelUnbondingDelegation` message allows delegators to cancel the `unbondingDelegation` entry and deleagate back to a previous validator.
+
++++ https://github.com/cosmos/cosmos-sdk/blob/28243eb41c16ecfc95631ac2bb266dd28ed5c317/proto/cosmos/staking/v1beta1/tx.proto#L36-L38
+
++++ https://github.com/cosmos/cosmos-sdk/blob/28243eb41c16ecfc95631ac2bb266dd28ed5c317/proto/cosmos/staking/v1beta1/tx.proto#L144-L154
+
++++ https://github.com/cosmos/cosmos-sdk/blob/28243eb41c16ecfc95631ac2bb266dd28ed5c317/proto/cosmos/staking/v1beta1/tx.proto#L156-L157
+
+
+This message is expected to fail if:
+* the `unbondingDelegation` entry is already processed.
+* the `cancel unbonding delegation` amount is greater than the `unbondingDelegation` entry balance.
+* the `cancel unbonding delegation` height doesn't exists in the `unbondingDelegationQueue` of the delegator.
+
+When this message is processed the following actions occur:
+* if the `unbondingDelegation` Entry balance is zero 
+   * in this condition `unbondingDelegation` entry will be removed from `unbondingDelegationQueue`.
+   * otherwise `unbondingDelegationQueue` will be updated with new `unbondingDelegation` entry balance and initial balance
+* the validator's `DelegatorShares` and the delegation's `Shares` are both increased by the message `Amount`.
+
 ## MsgBeginRedelegate
 
 The redelegation command allows delegators to instantly switch validators. Once

x/staking/spec/07_events.md

@@ -63,6 +63,18 @@ The staking module emits the following events:
 
 * [0] Time is formatted in the RFC3339 standard
 
+### MsgCancelUnbondingDelegation
+
+| Type                          | Attribute Key       | Attribute Value                     |
+| ----------------------------- | ------------------  | ------------------------------------|
+| cancel_unbonding_delegation   | validator           | {validatorAddress}                  |
+| cancel_unbonding_delegation   | delegator           | {delegatorAddress}                  |
+| cancel_unbonding_delegation   | amount              | {cancelUnbondingDelegationAmount}   |
+| cancel_unbonding_delegation   | creation_height     | {unbondingCreationHeight}           |
+| message                       | module              | staking                             |
+| message                       | action              | cancel_unbond                       |
+| message                       | sender              | {senderAddress}                     |
+
 ### MsgBeginRedelegate
 
 | Type       | Attribute Key         | Attribute Value       |

x/staking/spec/09_client.md

@@ -712,6 +712,19 @@ Example:
 ```bash
 simd tx staking unbond cosmosvaloper1gghjut3ccd8ay0zduzj64hwre2fxs9ldmqhffj 100stake --from mykey
 ```
+#### cancel unbond 
+The command `cancel-unbond` allow users to cancel the unbonding delegation entry and delegate back to the original validator.
+
+Usage:
+```bash
+simd tx staking cancel-unbond [validator-addr] [amount] [creation-height]
+```
+
+Example:
+```bash
+simd tx staking cancel-unbond cosmosvaloper1gghjut3ccd8ay0zduzj64hwre2fxs9ldmqhffj 100stake 123123 --from mykey
+```
+
 
 ## gRPC
 

x/staking/spec/README.md

@@ -42,6 +42,7 @@ network.
     * [MsgEditValidator](03_messages.md#msgeditvalidator)
     * [MsgDelegate](03_messages.md#msgdelegate)
     * [MsgUndelegate](03_messages.md#msgundelegate)
+    * [MsgCancelUnbondingDelegation](03_messages.md#msgcancelunbondingdelegation)
     * [MsgBeginRedelegate](03_messages.md#msgbeginredelegate)
 4. **[Begin-Block](04_begin_block.md)**
     * [Historical Info Tracking](04_begin_block.md#historical-info-tracking)