Use cargo-license-template

[cycraig]

Description of change

Use cargo-license-template as a replacement for the removed license_template_path feature of rustfmt.

Note that running cargo-license-template in the root of the workspace checks all sub-directories, including the Wasm and Stronghold bindings.

Links to any relevant issues

Fixes #921.

Type of change

• Chore (a non-breaking change which fixes an issue)

How the change has been tested

cargo install -f cargo-license-template
cargo license-template --template .license_template --ignore .license_template_ignore --verbose

Passes in CI too: https://github.com/iotaledger/identity.rs/actions/runs/3060562925/jobs/4939227569

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[olivereanderson]

Thanks for fixing this issue and for taking the time to explain that it works in CI too 👍

I also checked out this branch and tested it locally and I wasn't able to produce any unexpected behaviour.

Aside: I am curious whether it would be possible to make the tool check .ts files as well, but that might be beyond the scope of what the tool is designed for. Definitely not something that needs to be addressed in this PR.

Again thank you very much for working on this!

[cycraig]

possible to make the tool check .ts files as well

Not out-of-the-box, no. It's currently hardcoded for .rs files.
https://github.com/grtlr/cargo-license-template/blob/487d6ac59f318624693e74d8909c0e5e19876214/src/main.rs#L92