Updates an existing Channel

Custom fields (FieldName plus a human-facing Description) that become mandatory when creating a release in this channel. Omit to keep the current definitions; an empty list clears them.

Rules restricting which Git refs may be used for external Git dependencies referenced by deployment steps. Each rule targets step Git dependencies via GitDependencyActions (DeploymentActionSlug plus GitDependencyName) and lists the allowed Git reference patterns in Rules. Omit to keep the current rules; an empty list clears them.

Version rules restricting which package versions may be used when creating a release in this channel. Each rule targets step packages via ActionPackages (DeploymentAction is the step name or ID, PackageReference the package reference name or ID) and constrains versions with a NuGet-style VersionRange (e.g. '[1.0,2.0)') and/or a Tag regex matched against the package's pre-release tag (e.g. '^$' for stable versions only). Keep each existing rule's Id; leave it blank on new rules. Omit to keep the current rules; an empty list clears them.