fix: Use node representation for Block

[fredcarle]

Relevant issue(s)

Resolves #2745

Description

This PR ensures that the node being passed to the link system is in it's representation form. This will allow the use of optional fields.

Node that the 2 added block unit tests are there to cover when the optional isEncrypted field will be added to Block ipld schema.

Tasks

• I made sure the code is well commented, particularly hard-to-understand areas.
• I made sure the repository-held documentation is changed accordingly.
• I made sure the pull request title adheres to the conventional commit style (the subset used in the project can be found in tools/configs/chglog/config.yml).
• I made sure to discuss its limitations such as threats to validity, vulnerability to mistake and misuse, robustness to invalidation of assumptions, resource requirements, ...

How has this been tested?

make test

Specify the platform(s) on which this was tested:

• MacOS

[islamaliev]

Looks great. Thanks for a quick fix

[islamaliev]

question: I wonder where this ipld coming from. I don't see any import that ends with "ipld"

[fredcarle]

go-ipld-prime is the package 🙂

[nasdf]

LGTM.