service/block: Remove block fetching capability from BlockService

[renaynay]

This PR is the first step necessary to resolve #251 (it resolves the first TODO).

[Wondertan]

Btw, there should be a changelog entry for this one.

[Wondertan]

@adlerjohn, note that this PR is a part of a bigger goal and changes here might not make sense in isolation

[adlerjohn]

@Wondertan I gathered that much 😂. So long as the noted peculiarities are expected I have no issue with them temporarily existing.

[Wondertan]

Why utils?

I like the approach of making things reusable but in a modular domain-specific way, not a monolithic way. And we are already going with the former.

The latter:
services/
header_service.go
share_service.go

The former:
header/
service.go
share/
service.go

Same with utils. Having one big folder for all the utils is monolithic and prone to dependency cycles, as it depends on our data structures.

If this makes sense to you, pls move you the helper func inside a respective module/domain package.

[adlerjohn]

conflicts

[renaynay]

@adlerjohn closing this PR in favour of #317