Allow users to config AuthCodeEntropy

[nerocrux]

Is your feature request related to a problem? Please describe.

• I understand 32 bytes entropy may be secure enough, but in some cases I may still want to change the entropy (32 bytes -> 64 or 128 bytes) of Token generated using HMAC strategy, which is currently not possible.

Describe the solution you'd like

• Make AuthCodeEntropy configurable for NewOAuth2HMACStrategy()
  • https://github.com/ory/fosite/blob/master/compose/compose_strategy.go#L41

Describe alternatives you've considered

• None.

Additional context

• Maybe also should give this value a upper limit, like 256 (int).
• If this sounds OK, I'll create a pull request. Thanks for reviewing.

[aeneasr]

Yup sounds good

[nerocrux]

Thank you! I will implement this.

[nerocrux]

PR created.
#342

[nerocrux]

Implemented so I'm gonna close this issue.
Thanks!