Adds webhook TLS config info to the migration doc

Signed-off-by: Sagar Muchhal <[email protected]>

Author: srm09

docs/book/src/developer/providers/v1.2-to-v1.3.md

@@ -66,3 +66,7 @@ The default value is 0, meaning that the volume can be detached without any time
   The variable `SkipUpgrade` could be set to revert to the old behaviour by making use of the `KUBERNETES_VERSION` variable and skipping the kubernetes upgrade.
 - cert-manager upgraded from v1.9.1 to v1.10.0.
 - Machine `providerID` is now being strictly checked for equality when compared against Kubernetes node `providerID` data. This is the expected criteria for correlating a Cluster API machine to its corresponding Kubernetes node, but historically this comparison was not strict, and instead compared only against the `ID` substring part of the full `providerID` string. Because different providers construct `providerID` strings differently, the `ID` substring is not uniformly defined and implemented across providers, and thus the existing `providerID` equality can not guarantee the correct Machine-Node correlation. It is very unlikely that this new behavior will break existing providers, but FYI: if strict `providerID` equality will degrade expected behaviors, you may need to update your provider implementation prior to adopting Cluster API v1.3.
+- The default minimum TLS version in use by the webhook servers is 1.2.
+
+### Suggested changes for providers
+- Provider can expose the configuration of the TLS Options for the webhook server; it is recommended to use utility functions under the `util/flags` package to ensure consistency across CAPI and other providers.