Update upgrades.md

Added a section on the different releases and a section about the slow release

Author: krithika-ch

docs/cloud/manage/upgrades.md

@@ -39,7 +39,10 @@ You will not be charged for the time that the service is under maintenance. _Mai
 
 ## Release channels (upgrade schedule) {#release-channels-upgrade-schedule}
 
-You are able to specify the upgrade schedule for your ClickHouse Cloud service by subscribing to a specific release channel.
+You are able to specify the upgrade schedule for your ClickHouse Cloud service by subscribing to a specific release channel. There are three release channels and the ability to configure the day and time of the week for upgrades with Scheduled upgrades
+- Fast release channel for early access to upgrades, note the Basic tier services are automatically enlisted to the fast release channel
+- Regular release channel is the default and upgrades on this channel start two weeks aftet the Fast release channel upgrades. If your service on the Scale and Enteprise tier does not have a Release channel set, it is by default on the Regular release channel
+- Slow release channel is the deferred release and upgrades are spaced two weeks after the Regular release channel
 
 ### Fast release channel (early upgrades) {#fast-release-channel-early-upgrades}
 
@@ -76,6 +79,18 @@ Upgrades to the regular release channel are typically performed two weeks after
 Basic tier services are upgraded soon after the Fast release channel.
 :::
 
+### Slow release channel (deferred upgrades) {#slow-release-channel-deferred-upgrades}
+
+<EnterprisePlanFeatureBadge feature="The slow release channel"/>
+
+We offer a **Slow release** channel if you would like your services to receive upgrades after the regular release schedule.
+
+Specifically, services will:
+
+- Be upgraded after the Fast and Regular release channels rollouts are complete
+- Receive ClickHouse releases ~ 2 weeks after the regular release
+- Meant for customers that want additional time to test ClickHouse releases on their non production enviornments before the production upgrade. Non production environments can either get upgrades on the Fast or the Regular release channel for testing and validation
+
 ## Scheduled upgrades {#scheduled-upgrades}
 
 <EnterprisePlanFeatureBadge feature="Scheduled upgrades" linking_verb_are="true"/>