Fix block issuer key from bytes conversion

[PhilippGackstatter]

Description of change

Allow inputting an Ed25519 Public Key and use the hash of it as the block issuer key.

Links to any relevant issues

n/a

Type of change

Choose a type of change, and delete any options that are not relevant.

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

How the change has been tested

Describe the tests that you ran to verify your changes.

Make sure to provide instructions for the maintainer as well as any relevant configurations.

Change checklist

Tick the boxes that are relevant to your changes, and delete any items that are not.

• 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
• I have checked that new and existing unit tests pass locally with my changes

[Thoralf-M]

Thanks!