create-branch-protection-rule.graphql

# https://docs.github.com/en/graphql/reference/input-objects#createbranchprotectionruleinput
mutation CreateBranchProtectionRule($branchName: String!, $repositoryId: ID!) {
  createBranchProtectionRule(
    input: { pattern: $branchName, repositoryId: $repositoryId }
  ) {
    branchProtectionRule {
      id
      databaseId
    }
  }
}