feat: add client authentication strategy

[narg95]

Related issue

#564

Proposed changes

• Add a ClientAuthenticationStrategy type to provide an extension point for custom client authentication methods
• Add Fosite.DefaultClientAuthentication as fosite's default and backward compatible client authentication strategy. Its content is 100% the current fosite's client authentication logic
• Add method Fosite.WithDefaultClientAuthentication to use fosite's default client authentication strategy

Checklist

• I have read the contributing guidelines
  and signed the CLA.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got green light (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• [ x] I have added tests that prove my fix is effective or that my feature
  works.
• [x ] I have added necessary documentation within the code base (if
  appropriate).

[aeneasr]

Thank you, this makes sense to me!

However, I think it would make sense to have a small helper function like f.authenticateClient() which returns the default strategy unless another strategy was set. This will prevent potential panics for people who forget to call WithDefaultClientAuthentication

[narg95]

However, I think it would make sense to have a small helper function like f.authenticateClient() which returns the default strategy unless another strategy was set. This will prevent potential panics for people who forget to call WithDefaultClientAuthentication

great idea, it's done! Actually it made the pull request is even smaller

[aeneasr]

Awesome, thank you! 🎉 Your contribution makes Ory better :)

[aeneasr]

Oh, unfortunately, for some reason, the CircleCI tests are not running. Do you maybe have a fork on CircleCI of ory/fosite that you follow? If so, you need to unsubscribe / unwatch that fork. Then, you need to make another push to your branch using:

$ git commit --amend --allow-empty
$ git push --force

That should get the CI running! Thank you :)

[narg95]

It works now. I did nothing with CircleCI. I unsubscribed my branch from Travis-CI and amended the commit. One of the two made it work :)

[aeneasr]

Nice, thank you! :)