I am not using SonarQube local server, or SonarCloud, or SonarLint. I instead just reference the SonarAnalyzer.CSharp nuget package directly in each of my .NET Core projects and configure the rule severity using .editorconfig (more info)
How can I configure the license header format with this setup? By just setting the severity to 'error', the analyzer expects to see the default SQ license header.