Consent /reject without error data will always return an invalid_request error

[LaylBongers]

Describe the bug
When rejecting a consent request, but not including "error", "error_description" or "error_hint", the values that aren't given will default to a generic invalid_request error. This is completely inaccurate to what happened and very confusing while developing.

To Reproduce

1. Go through the OAuth2 authorization code flow until consent
2. Reject consent, but do not set any value for "error", "error_description" or "error_hint"
3. Read the resulting error in the callback

Expected behavior
The right behavior should probably be either passing an error that indicates the consent request was rejected, or a generic error. The invalid_request error sends the developer to the wrong place for debugging.

Version:

• Environment: Docker
• Version oryd/hydra:v1.0.0-rc.6_oryOS.10

[aeneasr]

Thank you! Feel free to PR :)