Allow users to bring their own template

[sahidvelji]

To maximize flexibility in code generation, allow a user to write their own template and supply the path to the template when using the generate command. This way, users are not bound to the existing templates such as https://github.com/open-feature/cli/blob/main/internal/generators/golang/golang.tmpl.

[beeme1mr]

This sounds like a good idea to me. I'd expect the implementation to be relatively straightforward. What did you have in mind for the subcommand? Something like openfeature generate custom --template ./cobal.tmpl

[sahidvelji]

I don't think a subcommand is needed in this case. We could just add a new flag. Something like this:

  --template string   Path to a custom template. If not specified, the default template is used.

Usage:

openfeature generate go --template ./openfeature-go.tmpl

[sahidvelji]

We should also have documentation that provides guidance on how to write a custom template.

[twu]

@sahidvelji 👋 I took a stab at supporting custom templates via --template flag. Hope this is okay. See #198