add changelog entries

.changelog/unreleased/api-breaking/2400-preccv.md

@@ -0,0 +1,12 @@
+- Enable existing (standalone) chains to use the existing client (and connection)
+  to the provider chain when becoming a consumer chain. This feature introduces 
+  the following API-breaking changes.
+  ([\#2400](https://github.com/cosmos/interchain-security/pull/2400))
+
+  - Add `connection_id` and `preCCV` to `ConsumerGenesisState`, the consumer 
+  genesis state created by the provider chain. If the `connection_id` is not empty,
+  `preCCV` is set to true and both `provider.client_state` and `provider.consensus_state`
+  are set to nil (as the consumer doesn't need to create a new provider client).
+  As a result, for older versions of consumers, the `connection_id` in 
+  `ConsumerInitializationParameters` must be empty and the resulting `ConsumerGenesisState`
+  needs to be adapted, i.e., both `connection_id` and `preCCV` need to be removed. 

.changelog/unreleased/features/2400-preccv.md

@@ -0,0 +1,13 @@
+- Enable existing (standalone) chains to use the existing client (and connection)
+  to the provider chain when becoming a consumer chain. This feature introduces 
+  the following changes.
+  ([\#2400](https://github.com/cosmos/interchain-security/pull/2400))
+
+  - Add `connection_id` to `ConsumerInitializationParameters`, the ID of 
+  the connection end _on the provider chain_ on top of which the CCV channel will 
+  be established. Consumer chain owners can set `connection_id` to a valid ID in 
+  order to reuse the underlying clients.
+  - Add `connection_id` to the consumer genesis state, the ID of the connection 
+  end _on the consumer chain_ on top of which the CCV channel will be established.
+  If `connection_id` is a valid ID, then the consumer chain will use the underlying 
+  client as the provider client and it will initiate the channel handshake.

.changelog/unreleased/state-breaking/2400-preccv.md

@@ -0,0 +1,3 @@
+- Enable existing (standalone) chains to use the existing client (and connection)
+  to the provider chain when becoming a consumer chain.
+  ([\#2400](https://github.com/cosmos/interchain-security/pull/2400))

docs/docs/build/modules/02-provider.md

@@ -1553,6 +1553,7 @@ init_params:
   spawn_time: "2024-09-26T06:55:14.616054Z"
   transfer_timeout_period: 3600s
   unbonding_period: 1209600s
+  connection_id: ""
 metadata:
     description: description of your chain and all other relevant information
     metadata: some metadata about your chain
@@ -1708,7 +1709,8 @@ where `update-consumer-msg.json` contains:
       "consumer_redistribution_fraction": "0.75",
       "blocks_per_distribution_transmission": "1500",
       "historical_entries": "1000",
-      "distribution_transmission_channel": ""
+      "distribution_transmission_channel": "",
+      "connection_id": ""
   },
   "power_shaping_parameters":{
       "top_N": 0,

x/ccv/provider/client/cli/tx.go

@@ -245,7 +245,8 @@ where create_consumer.json has the following structure:
     "consumer_redistribution_fraction": "0.75",
     "blocks_per_distribution_transmission": 1000,
     "historical_entries": 10000,
-    "distribution_transmission_channel": ""
+    "distribution_transmission_channel": "",
+	"connection_id": ""
   },
   "power_shaping_parameters": {
     "top_N": 0,
@@ -344,7 +345,8 @@ where update_consumer.json has the following structure:
     "consumer_redistribution_fraction": "0.75",
     "blocks_per_distribution_transmission": 1000,
     "historical_entries": 10000,
-    "distribution_transmission_channel": ""
+    "distribution_transmission_channel": "",
+	"connection_id": ""
    },
    "power_shaping_parameters": {
     "top_N": 0,